The death toll from the blaze that gutted an Oakland, California warehouse reached 36 on Monday, and could climb further as investigators continue to search the building where an electronic dance party turned into an inferno.
Officials say that so far only about 20 percent of the building has been searched. One local fire official, Melinda Dayton, said, "This will be a long and arduous process, but we want to make sure we are respecting the victims and their families and firefighter safety."
WATCH: Drayton on fire investigation
Fire ripped through the cluttered warehouse late Friday that had been cobbled into artist studios. There was no permit for it to be used as a living space, nor for entertainment.
The structure was known as the "Ghost Ship." Officials said the only way down from the second story was a stairwell constructed entirely of wooden pallets. Victims range in age from teenagers to 30-plus year-olds.
Officials have yet to determine how the fire started in a building that was not equipped with sprinklers. Arson investigators are combing through the charred premises.
"It appears that either you got out or you got trapped inside," said Alameda County Sheriff's Office spokesman Sergeant Ray Kelly.
It took 55 firefighters about four hours to bring the fire under control, Battalion Chief Lisa Baker told the local newspaper, the East Bay Times.
Oakland Fire Chief Teresa Deloche-Reed said the roof of the building collapsed, further complicating the search effort.
"Right now, there's limited access to the structure, but it's too unsafe. And not only that, there's a lot of heavy wood from when the roof came in that's going to have to be removed,” she told reporters. “So it's going to take us a while to finish up the search.”
Firefighters used chain saws and axes to cut through the debris.
According to officials, the building was home to about 50 people who lived in an artists’ collective, and a Facebook page for the event showed that 176 people planned to attend the party.
After repeated complaints from neighbors that people were illegally living in the building and trash was piling up, the city of Oakland opened an investigation on November 13. Officials went to inspect the property four days later but could not get inside.