Fire investigators say they were unable to determine what caused the blaze at the Oakland, California, warehouse that killed 36 people last December.
Investigators say they cannot rule out an electrical failure, candles, incense, smoking material or an open flame as possible causes.
According to a report posted late Monday on the city of Oakland's website, the fire originated on a back corner on the ground floor of the two-story building. But investigators say they couldn't determine a cause because of the extensive fire damage.
The report by federal and local officials says at first, firefighters had no idea how many people were inside the warehouse, or that it was the site of a concert that night or there so many flammable objects scattered throughout the two story building, that had been turned into a living compound.
The report says as firefighters arrived "nobody seemed excited or distraught."
Firefighters entering the building soon were blinded by smoke and had to follow their hoses to find their way out, the report says. They went back in awhile later, but the "fire flashed out the south side, and three windows blew out ... at this point they all pulled out and went defensive," the report says
Seven bodies were found on the second floor, 29 on the ground floor in clusters, some underneath the collapsed roof, the report says.
Jennifer Fiore, along with Mary Alexander, represents families of several of the deceased and five survivors.
"We are suing the owner, the master tenant, as well as producers and performers that evening and the others that had worked on the electrical equipment," Fiore said.
Earlier this month, prosecutors charged two people with 36 counts of manslaughter, saying Derick Almena rented out space in the illegally converted warehouse and Max Harris planned the unpermitted party held the night of the blaze.