Provide the highlights for the following article:\n    (CNN) -- Six of the seven college students killed in a massive house fire Sunday morning in Ocean Isle Beach, North Carolina, attended the University of South Carolina, a university official said Sunday. \"This is a very sad day for the University of South Carolina family,\" NAME_1, the vice president for student affairs, told reporters. The seventh fatality is believed to be a Clemson University student, he said. The six survivors -- who were treated and released from Brunswick Community Hospital -- are also USC students, he said. NAME_2 said the bodies were being sent to Chapel Hill, North Carolina, for identification.  Watch home video showing the house in flames \u00bb . \"It is difficult to ascertain exactly who was in the house and who was not,\" NAME_2 said, explaining that several area houses were filled with college students visiting for the weekend. Newspaper deliveryman NAME_3 was aghast when he first saw the inferno early Sunday morning. He tried to approach the door but the flames were too intense, he told the Associated Press. \"When I was going up to the entryway, you could hear the windows above me explode,\" NAME_4 said. \"When I knew the flames had taken over, I don't think I've ever felt as helpless in my life.\" The USC students were affiliated with the Delta Delta Delta sorority and the Sigma Alpha Epsilon fraternity, NAME_2 said, although he stressed that the weekend was not an official Greek function. \"It just so happens, as on many university campuses, that certain sororities and certain fraternities hang around together,\" he said. One person described as \"unaccounted for\" was later confirmed dead, Ocean Isle Beach Mayor NAME_5 told CNN. \"We suffered a terrible tragedy at Ocean Isle this morning,\" NAME_6 said in a news conference. \"Nothing like this has ever happened at Ocean Isle Beach, and we hope it never will again.\" She said officials had not yet contacted all the victims' families, and that they were not yet releasing their names. The mayor said one of the 13 people in the house was related to the house's owner. NAME_6 said the house was fully \"engulfed\" in flames around 7 a.m. when the fire department arrived on the scene, about five minutes after the fire department was notified. She said the house had working smoke detectors, AP reported. Officials are investigating the cause of the fire, NAME_6 said. \"We ran down the street to get away,\" NAME_7 told the AP. The University of North Carolina student 