It could take fire investigators days to determine what caused an intense fire that ripped through a two-apartment house near the University of Southern Maine, as officials worked to identify the five people who were killed.

Portland Fire Chief Jerry LaMoria said the investigation was in a preliminary stage and it could take several days before officials know how the state's deadliest fire in three decades started. Investigators will be looking to see if there were any code violations at the 94-year-old house.

State fire marshal's spokesman Steve McCausland said Sunday most, if not all, the residents were USM students, but he said there was no indication that students were killed in the fire.

Two bodies were found on the second floor and three on the third floor. Everyone who had been in the house was accounted for, officials said.

The one person critically injured in the fire was identified as 29-year-old Steven Summers of Rockland. McCausland said Summers was visiting friends at the house when the fire broke out Saturday morning following a Halloween party the night before. Summers was in Massachusetts General Hospital on Sunday, where he was being treated for severe burns. There were reports that he jumped out of a second-story window to escape the flames.

Fire investigators went through what remained of the three-story building, searching for clues to the cause of the fire. Outside, the road was still blocked off Sunday and a memorial had sprung up that included flowers and a pumpkin.

David Bragdon Sr. of Rockland feared his son, 27-year-old David Bragdon Jr., was among the victims. The younger Bragdon lived in the home, worked at the nearby Great Lost Bear restaurant and hasn't been heard from since the fire.

Bragdon, his eyes filling with tears, talked to reporters outside the house, saying: "Is it true? Is it real? It's hard not knowing 100 percent."

He said he has questions about the condition of the house, including whether smoke alarms were working.

Carol Schiller, who lives near the home and is president of the University Neighborhood Organization, said she woke up Saturday morning to loud popping sounds and looked outside her window to see a man engulfed in flames.

"He was making some sounds, probably screaming," Schiller said. "I saw him rolling on the ground and then it clicked, 'Oh my god, he's on fire.'"

Schiller said she wrote a letter to the city in May expressing concern about the condition of the house. She said there were often many garbage bags left on the porch and she feared there were too many people living in the building.

The mood in the neighborhood was solemn Sunday as friends, family members and strangers stopped by to see the destroyed home and leave flowers.

"It's feels like you're walking around a grave site," said Jackie Reis, a 27-year-old USM graduate who lives down the street.

Reis said she didn't know the people who lived there personally but saw them frequently and they were always friendly.

The old house looked messy and needed repairs, but "it didn't seem like anyone was being reckless," she said.

Another person who was injured was treated at a hospital and released; seven people escaped from the burning building. University President David Flanagan said at least one of the people who escaped was a student.

The fire, Maine's deadliest since a 1984 blaze killed five in Hartland, ripped a hole through the roof of the house and both apartment units were badly burned. The neighborhood is a dense, residential area of single and multi-family homes where full-time residents and students live.

The Portland Press Herald reported the house is owned by Gregory Nisbet. A phone number listed in his name was out of service and nobody answered the door at his home on Sunday.