By . Daily Mail Reporter . UPDATED: . 14:29 EST, 10 September 2011 . As power was finally restored to six . million, officials from Arizona's largest electric utility said on . Friday they are still baffled by the chain of events that caused massive . blackouts across Arizona, California and parts of Mexico. APS has said they believe a single . employee at the North Gila substation tripped a 500-kV transmission line . that runs from Arizona to Southern California. They are investigating how that happened and the subsequent failure of safeguards that should have prevented major outages. Scroll down for video . Darker than usual: Despite lights showing in San Diego buildings, the city was without power after a blackout on caused havoc on Thursday . Daniel Froetscher, Vice President of . Energy Delivery for APS, said: 'We’re struggling. We have to take a hard . look at the system design and figure out exactly what happened. We . don’t know the underlying causes.' Early Thursday, APS officials noticed . an issue with a series capacitor at the North Gila substation outside . the city of Yuma, Mr Froetscher said. The capacitor — a piece of equipment . about the size of a small car that helps the utility manage voltage — . wasn’t functioning properly. APS personnel were dispatched to take it offline, the LA Times. Going nowhere: Passenger Michael Moretti waits at the baggage pick-up at San Diego International Airport after a massive blackout hit Southern California . Typically, the utility can shut down an individual capacitor and reroute power without any disruption of service, Mr Froetscher said. But this time, something went wrong. After the North Gila capacitor was taken offline, the 500-kV line that runs through the substation went down. At that point, 3.27pm, the grid should have compensated for the loss of the 500-kV line, which runs from Yuma to the Imperial Valley and San Diego. 'The intent is for the system to automatically open and close different breakers and relays and switches to reroute power from the line that was lost to other lines to continue to provide service,' he said. 'Transmission lines do go out of service on an unplanned basis; it’s not an unusual event. Most times when a line goes out unexpectedly, the system performs exactly as it’s expected to and customers never know the difference.' Rebecca Wilder, a spokeswoman for the Arizona Corporation Commission, which regulates electric utilities in the state, said the agency was monitoring the APS investigation. Stephanie McCorkle, a spokeswoman for the California Independent System Operator, which operates most of the state’s electric grid, insisted that it’s too early to even theorize about the cause of the San Diego power outage or its size. 'Someone who comes to conclusions quickly doesn’t know what he is talking about,' she said, noting that a similar massive outage struck parts of California on August 10, 1996, with the loss of a 500-kV high-voltage transmission line from the Pacific Northwest that is similar to the Southwestern Power Link that went down Thursday in Arizona. The blackout was a reminder that U.S. transmission lines remain vulnerable to cascading power failures. There have been several similar failures in recent years. In 2003, a blackout knocked out power to 50 million people in the Midwest and the Northeast. And in 2005, a major outage struck the Los Angeles metropolitan area, the Associated Press reports. That same year, Congress required utilities to comply with federal reliability standards for the electricity grid, instead of self-regulation. Layers of safeguards and backups were intended to isolate problems and make sure the power keeps flowing. But that didn't happen on Thursday. By candlelight: The power outage didn't end the night for visitors to Voyeur in San Diego's Gaslamp District . The San Diego County Sheriff's Department and other police departments told 10News.com  they received reports of break-ins and vandalism at homes and businesses. The Sheriff's department received reports of a glass door broken at a taco store in Lemon Grove and a report of a home break-in in Vista during the outage. A suspect in San Diego was arrested after he was found to have items from a Kensington area home where neighbours had reported a possible robbery. APS, Arizona's largest electricity provider, said a utility worker doing maintenance near Yuma triggered the blackout. The error, on a high-voltage power line linking Arizona and San Diego, causing a cascading series of electrical grid failures stretching into Southern California. Authorities say the outage was accidentally triggered sometime Thursday afternoon when the APS electrical worker removed a piece of monitoring equipment at a power substation in southwest Arizona. An APS statement said: 'The outage appears to be related to a procedure an APS employee was carrying out in the North Gila substation. Lights out: Buildings in downtown San Diego look eerily abandoned as the blackout drags on. A single worker was responsible for the power cut . Inconvenience store: A shopper is forced to make her grocery choices in the dark at her local store. More than six million people and businesses were affected . 'Operating and protection protocols . typically would have isolated the resulting outage to the Yuma area. The . reason that did not occur in this case will be the focal point of the . investigation into the event, which already is underway.' Daniel Froetscher, an APS vice president, said authorities . quickly ruled out any sabotage or, in the anxious days leading up to . the 10th anniversary of Sept. 11 attacks, any suggestion of terrorism. Power tripped: Map shows the affected areas of the power outage . 'This was not a deliberate act. The employee was just switching out a piece of equipment that was problematic.' For obvious reasons, APS did not name the employee. It's possible that extreme heat in the region also may have caused some problems with the transmission lines, one expert said. Many minor traffic accidents occurred as the outage caused mayhem on streets without stoplights during rush hour. Leah Walden, 59, of California, said she saw about five fender-bender crashes on one trip out. Ms Walden said: 'People are irritated. They don't want to wait.' In the beach town of Encinitas north of San Diego, Tim Grenda, 41, put a positive spin on the situation, pointing out that his hot yoga class was cooler as a result of the outage. Rosa Maria Gonzales, a spokeswoman with the Imperial Irrigation District in California's sizzling eastern desert, was less enthusiastic - temperatures were well into triple-digit territory when the power went out. Ms Gonzales said: 'It feels like you're in an oven and you can't escape.' Many offices closed during the outage but workers were caught in gridlock conditions because traffic lights were out. Early Friday morning, power was on the way to being restored for some six million people affected by the outage. Nearly . 700,000 of the 1.4million customers who lost power Southern California . saw their lights come on at about 2:45am local time, the Los Angeles . Times reported. Hospital . emergency rooms switched to backup generators, while police stations . also had to rely on generators to accept emergency calls across the area . and officers struggled to direct traffic at intersections where signals . were out. The blackout extended from southern . Orange County to San Diego to Yuma, Arizona. It is also affecting cities . south of the border, with much of the state of northern Baja in . darkness. Stock up: People line up outside an Encitas, California, 7-Eleven store to pick up supplies . Over the border: Even the city of Tijuana, in the Mexican state of Baja California, was affected - with only the lights of cars visible throughout the city . Residents were left sweltering in the late-summer heat. In the moonlight: Even Mexico was affected by the outage, cutting power to buildings in Tijuana . 'It . feels like you're in an oven and you can't escape,' said Rosa Maria . Gonzales, a spokeswoman with the Imperial Irrigation District in . California's sizzling eastern desert. It was about 115 degrees when the power went out for about 150,000 of its customers, she said. FBI officials ruled out terrorism . while power plant authorities struggled to find the cause of the outage . that started shortly before 4pm local time. A . transmitter line between Arizona and California was severed, said Mike . Niggli, chief operating officer of San Diego Gas & Electric Co., . causing the outage. The extreme heat in some areas also may have caused . some problems with the lines. People were trapped in elevators and on rides at Sea World in San Diego and Legoland in Carlsbad. The San Onofre nuclear power plant . went offline at 3.30pm as they are programmed to do when there is a . disturbance in the power grid, said Charles Coleman, a spokesman from Southern California Edison. He said there was no danger to the public or to workers there. The . outage came more than eight years after a more severe black out in 2003 . darkened a large swath of the Northeast and Midwest. More than 50 million people were affected in that outage. Five . hundred to 2,000 SoCal Edison customers in southern Orange County and . Riverside County are currently without power and there is no estimate . for when power will be restored, Coleman said. A pain at the pump: People park their cars at an Encinitas, California, gas station, waiting for the power to come back on last night . She show must go on: Undaunted by the power cut, workers at Filippi's pizza still manage to serve customers by candlelight outside the store . Slow progress in all directions: Freeway traffic was gridlocked in both directions as traffic signals went down and police struggled to keep vehicles moving . Capt. Mike Stone of the Orange County Fire Authority said several people were trapped and rescued at the tony Ritz Carlton hotel in south Orange County, Stone said. In southern Orange County, the sheriff's department dispatched deputies to busy intersections because traffic lights were out, said John McDonald, a sheriff's spokesman. Outages were confirmed in San Clemente, San Juan Capistrano and Laguna Hills, he said.
Authorities say a worker triggered the blackout when he removed a piece of monitoring equipment at a power substation .
Power now fully restored for affected residents in Southern California, Arizona and Mexico by Saturday morning .
Vandalism and robberies reported at San Diego-area homes and businesses .
Minor traffic accidents reported as outage caused mayhem on streets without stoplights .
By . Daily Mail Reporter . UPDATED: . 14:29 EST, 10 September 2011 . As power was finally restored to six . million, officials from Arizona's largest electric utility said on . Friday they are still baffled by the chain of events that caused massive . blackouts across Arizona, California and parts of Mexico. APS has said they believe a single . employee at the North Gila substation tripped a 500-kV transmission line . that runs from Arizona to Southern California. They are investigating how that happened and the subsequent failure of safeguards that should have prevented major outages. Scroll down for video . Darker than usual: Despite lights showing in San Diego buildings, the city was without power after a blackout on caused havoc on Thursday . Daniel Froetscher, Vice President of . Energy Delivery for APS, said: 'We’re struggling. We have to take a hard . look at the system design and figure out exactly what happened. We . don’t know the underlying causes.' Early Thursday, APS officials noticed . an issue with a series capacitor at the North Gila substation outside . the city of Yuma, Mr Froetscher said. The capacitor — a piece of equipment . about the size of a small car that helps the utility manage voltage — . wasn’t functioning properly. APS personnel were dispatched to take it offline, the LA Times. Going nowhere: Passenger Michael Moretti waits at the baggage pick-up at San Diego International Airport after a massive blackout hit Southern California . Typically, the utility can shut down an individual capacitor and reroute power without any disruption of service, Mr Froetscher said. But this time, something went wrong. After the North Gila capacitor was taken offline, the 500-kV line that runs through the substation went down. At that point, 3.27pm, the grid should have compensated for the loss of the 500-kV line, which runs from Yuma to the Imperial Valley and San Diego. 'The intent is for the system to automatically open and close different breakers and relays and switches to reroute power from the line that was lost to other lines to continue to provide service,' he said. 'Transmission lines do go out of service on an unplanned basis; it’s not an unusual event. Most times when a line goes out unexpectedly, the system performs exactly as it’s expected to and customers never know the difference.' Rebecca Wilder, a spokeswoman for the Arizona Corporation Commission, which regulates electric utilities in the state, said the agency was monitoring the APS investigation. Stephanie McCorkle, a spokeswoman for the California Independent System Operator, which operates most of the state’s electric grid, insisted that it’s too early to even theorize about the cause of the San Diego power outage or its size. 'Someone who comes to conclusions quickly doesn’t know what he is talking about,' she said, noting that a similar massive outage struck parts of California on August 10, 1996, with the loss of a 500-kV high-voltage transmission line from the Pacific Northwest that is similar to the Southwestern Power Link that went down Thursday in Arizona. The blackout was a reminder that U.S. transmission lines remain vulnerable to cascading power failures. There have been several similar failures in recent years. In 2003, a blackout knocked out power to 50 million people in the Midwest and the Northeast. And in 2005, a major outage struck the Los Angeles metropolitan area, the Associated Press reports. That same year, Congress required utilities to comply with federal reliability standards for the electricity grid, instead of self-regulation. Layers of safeguards and backups were intended to isolate problems and make sure the power keeps flowing. But that didn't happen on Thursday. By candlelight: The power outage didn't end the night for visitors to Voyeur in San Diego's Gaslamp District . The San Diego County Sheriff's Department and other police departments told 10News.com  they received reports of break-ins and vandalism at homes and businesses. The Sheriff's department received reports of a glass door broken at a taco store in Lemon Grove and a report of a home break-in in Vista during the outage. A suspect in San Diego was arrested after he was found to have items from a Kensington area home where neighbours had reported a possible robbery. APS, Arizona's largest electricity provider, said a utility worker doing maintenance near Yuma triggered the blackout. The error, on a high-voltage power line linking Arizona and San Diego, causing a cascading series of electrical grid failures stretching into Southern California. Authorities say the outage was accidentally triggered sometime Thursday afternoon when the APS electrical worker removed a piece of monitoring equipment at a power substation in southwest Arizona. An APS statement said: 'The outage appears to be related to a procedure an APS employee was carrying out in the North Gila substation. Lights out: Buildings in downtown San Diego look eerily abandoned as the blackout drags on. A single worker was responsible for the power cut . Inconvenience store: A shopper is forced to make her grocery choices in the dark at her local store. More than six million people and businesses were affected . 'Operating and protection protocols . typically would have isolated the resulting outage to the Yuma area. The . reason that did not occur in this case will be the focal point of the . investigation into the event, which already is underway.' Daniel Froetscher, an APS vice president, said authorities . quickly ruled out any sabotage or, in the anxious days leading up to . the 10th anniversary of Sept. 11 attacks, any suggestion of terrorism. Power tripped: Map shows the affected areas of the power outage . 'This was not a deliberate act. The employee was just switching out a piece of equipment that was problematic.' For obvious reasons, APS did not name the employee. It's possible that extreme heat in the region also may have caused some problems with the transmission lines, one expert said. Many minor traffic accidents occurred as the outage caused mayhem on streets without stoplights during rush hour. Leah Walden, 59, of California, said she saw about five fender-bender crashes on one trip out. Ms Walden said: 'People are irritated. They don't want to wait.' In the beach town of Encinitas north of San Diego, Tim Grenda, 41, put a positive spin on the situation, pointing out that his hot yoga class was cooler as a result of the outage. Rosa Maria Gonzales, a spokeswoman with the Imperial Irrigation District in California's sizzling eastern desert, was less enthusiastic - temperatures were well into triple-digit territory when the power went out. Ms Gonzales said: 'It feels like you're in an oven and you can't escape.' Many offices closed during the outage but workers were caught in gridlock conditions because traffic lights were out. Early Friday morning, power was on the way to being restored for some six million people affected by the outage. Nearly . 700,000 of the 1.4million customers who lost power Southern California . saw their lights come on at about 2:45am local time, the Los Angeles . Times reported. Hospital . emergency rooms switched to backup generators, while police stations . also had to rely on generators to accept emergency calls across the area . and officers struggled to direct traffic at intersections where signals . were out. The blackout extended from southern . Orange County to San Diego to Yuma, Arizona. It is also affecting cities . south of the border, with much of the state of northern Baja in . darkness. Stock up: People line up outside an Encitas, California, 7-Eleven store to pick up supplies . Over the border: Even the city of Tijuana, in the Mexican state of Baja California, was affected - with only the lights of cars visible throughout the city . Residents were left sweltering in the late-summer heat. In the moonlight: Even Mexico was affected by the outage, cutting power to buildings in Tijuana . 'It . feels like you're in an oven and you can't escape,' said Rosa Maria . Gonzales, a spokeswoman with the Imperial Irrigation District in . California's sizzling eastern desert. It was about 115 degrees when the power went out for about 150,000 of its customers, she said. FBI officials ruled out terrorism . while power plant authorities struggled to find the cause of the outage . that started shortly before 4pm local time. A . transmitter line between Arizona and California was severed, said Mike . Niggli, chief operating officer of San Diego Gas & Electric Co., . causing the outage. The extreme heat in some areas also may have caused . some problems with the lines. People were trapped in elevators and on rides at Sea World in San Diego and Legoland in Carlsbad. The San Onofre nuclear power plant . went offline at 3.30pm as they are programmed to do when there is a . disturbance in the power grid, said Charles Coleman, a spokesman from Southern California Edison. He said there was no danger to the public or to workers there. The . outage came more than eight years after a more severe black out in 2003 . darkened a large swath of the Northeast and Midwest. More than 50 million people were affected in that outage. Five . hundred to 2,000 SoCal Edison customers in southern Orange County and . Riverside County are currently without power and there is no estimate . for when power will be restored, Coleman said. A pain at the pump: People park their cars at an Encinitas, California, gas station, waiting for the power to come back on last night . She show must go on: Undaunted by the power cut, workers at Filippi's pizza still manage to serve customers by candlelight outside the store . Slow progress in all directions: Freeway traffic was gridlocked in both directions as traffic signals went down and police struggled to keep vehicles moving . Capt. Mike Stone of the Orange County Fire Authority said several people were trapped and rescued at the tony Ritz Carlton hotel in south Orange County, Stone said. In southern Orange County, the sheriff's department dispatched deputies to busy intersections because traffic lights were out, said John McDonald, a sheriff's spokesman. Outages were confirmed in San Clemente, San Juan Capistrano and Laguna Hills, he said.
linking Arizona and San Diego, causing a stretching into Southern California. Authorities say the outage was accidentally triggered electrical worker removed a piece of monitoring equipment at a power substation in southwest said. Many minor traffic accidents occurred as the outage caused mayhem on streets without moonlight: Even Mexico was affected by the Hills, he said.