(Reuters) - Police on Monday searched the ocean off California and highways for three children missing since the sport-utility vehicle carrying their large family plunged off a cliff, killing at least six people in what may have been an intentional crash.

The family's wrecked GMC Yukon was discovered last Monday below the scenic California coastal cliff, only three days after child welfare authorities in their home state of Washington opened an investigation into allegations the children were being neglected, police and social services said.

According to court records, the family had troubles in the past when one of its two white mothers was charged with domestic assault against one of their six adopted black children.

The Hart family gained attention in 2014 after one of the children, Devonte, was photographed crying in the arms of a white police officer at a protest after the fatal police shooting of an unarmed black teenager in Ferguson, Missouri.

Driver Jennifer Hart, 38, and Sarah Hart, 38, a married couple from Washington state, were killed. So were at least three of their six adopted children, Markis, 19, Jeremiah, 14, and Abigail, 14, police said.

The bodies of their three other children, Hannah, 16, Devonte, 15, and Sierra, 12, were not recovered, but officials have said they believed all the children were in the vehicle and the other bodies may have been washed into the ocean.

"The search for the additional three children belonging to the family continues both at the scene, through water rescue and recovery, and other locations including routes of travel," the California Highway Patrol said in a statement. "This situation may have been an intentional act and not the result of a traffic collision."

The SUV appears to have stopped at a dirt pull-off area about 70 feet (21 meters) from the cliff at the edge of California's coastal Highway 1 in Mendocino County, about 180 miles (290 km) north of San Francisco, according to the vehicle's on-board computer.

It then accelerated over the edge, leaving no skid marks or other indications of a collision, the statement said. The SUV fell into rocks and was found partially submerged about 100 feet (30 meters) below the highway.

Police searched the family's home in Woodland, Washington, about 500 miles (805 km) north of the crash site, but found no suicide note.

The Washington State Department of Social and Health Services said it opened an investigation into the family for potential child neglect or abuse after a complaint on March 23.

Neighbors Dana and Bruce DeKalb told the Oregonian newspaper that Devonte had asked them for food for himself and his siblings after his parents withheld it as punishment. The DeKalbs did not respond to requests for comment.

Sarah Hart was convicted of misdemeanor domestic assault of Abigail in 2011 in Minnesota. Court documents show that one of the children, Abigail, told a teacher: "Mom hit me." </s> A special coroner's jury has determined that the couple who drove themselves and their six adopted children off a northern California cliff last year did so deliberately.

The jury's verdict of murder-suicide on Thursday confirms authorities' suspicions that the March 2018 crash was intentional. It also concludes thousands of hours of investigation into the widely publicized deaths of Sarah and Jennifer Hart and their children.

Presenting the findings from two days of testimony, Mendocino County Sheriff- Coroner Thomas Allman told reporters that he would accept the jury's ruling.

"It is my belief that both Jennifer and Sarah succumbed to a lot of pressure," sheriff's Lt. Shannon Barney said on Thursday, The Associated Press reports. "Just a lot of stuff going on in their lives, to the point where they made this conscious decision to end their lives this way and take their children's lives."

Authorities said the crash occurred in the days after the married couple took their children and fled their home following a visit from social services authorities, AP reports. Neighbors had filed a complaint stating that the children were being deprived of food by their parents.

A witness who was camping near where the vehicle drove off the cliff, along California's Highway 1, said he heard sounds of a car revving up and accelerating early in the morning on March 26, AP reports.

Later that day, a passing motorist reported the family's smashed GMC Yukon at the bottom of the cliff.

The California Highway Patrol said at the time that there was reason to believe the crash was intentional. Police determined that there were no brake marks where the vehicle accelerated and drove over the cliff, The Washington Post reports.

The bodies of the women and three of their children – Markis, Jeremiah and Abigail – were found inside and around the vehicle on the rocky shore. The remains of two other children — Ciera and Hanna – were also recovered later.

The body of the last child, Devonte, has not been found. Devonte had made headlines several years prior as the young black child pictured crying and embracing a white police officer during a Ferguson-related protest.

"I'm certainly aware of a contingent of citizens who have a belief that Devonte was not in the car," Allman said Thursday. "It is our opinion and the jury's opinion that he lived with his family and unfortunately he perished with his family."

CHP investigator Jake Slates told the jury that Sarah Hart had searched for information on suicide, drowning and overdose methods with her phone. Slates also said that Jennifer Hart, the driver, had a blood alcohol level over the legal driving limit, AP reports, and Sarah and the children had high amounts of generic Benadryl in their systems.

Another crash investigator with CHP, Timothy Roloff, said he had examined the vehicle's computerized data recorder and determined that the vehicle accelerated rapidly before the crash, according to The San Francisco Chronicle.

Authorities pointed out that, since there's no prosecution involved in the case, the jury's verdict can help bring closure to those who were close to the Hart family, as well as the investigators themselves.

"The blood relatives and adopted relatives of the entire family," Allman said. "Those are the people who I certainly want to tell you that our hearts are with you."
A same-sex couple and three of their adopted children have been found dead at the bottom of a cliff at the coast of northern California, along with the wreckage of their SUV. After further investigation, authorities eventually deduced that it was very likely that the couple, which was previously known to have abused their children, intentionally drove off the cliff with them.