SAN FRANCISCO, Dec. 4 (Xinhua) -- Officials in Oakland, California, said Sunday that 33 bodies have been found after warehouse fire occurred Friday night.

Authorities said the loft building did not have permits and investigators have not found the course of the fire.

Sergeant Ray Kelly of Alameda County Sheriff's Office said about 20 percent of the warehouse, which was burnt out by a fire starting about 11:30 p.m. on Friday, had been searched.

Heavy machinery was brought in to the site on Saturday to help with cleaning up the debris and shore up the structure, designated only as a warehouse but turned into a party venue and probably a residence.

Officials initially said firefighters found nine victims of the blaze, which took place during an electronic music party in the two-story building in an industrial neighborhood in the Bay Area city east of San Francisco.

In a previous press conference, Kelly said he did not know how many people were in the building, and how many left, meaning that there was no exact number of people unaccounted for. On Sunday, he said the number could rise, as well as the death toll.

The building is now a crime scene investigated by local and federal law enforcement agencies. Oakland mayor Libby Schaaf pledged a full investigation into the incident.