USviewer: The cause of the blaze and precise number of casualties remained undetermined hours after flames engulfed the two-story, structure that occupied about half a city block and housed a cluttered warren of artists' studios, craft booths, antiques and furniture.
The blaze started at about 11:30 p.m. on Friday in the city's Fruitvale district, a mostly Latino, blue-collar area that is also home to many artists living and working in converted lofts.
Oakland and Alameda County officials said they expected to find more victims once the burned-out ruins of the building were fully shored up and recovery crews were able to safely comb through the structure's charred interior.
City Fire Chief Teresa Deloach Reed, said the blaze marked the worst single-structure fire she had seen in her career. Mayor Libby Schaaf called it a "devastating scene."
Shaken friends of the missing huddled at a nearby pub waiting for word on possible victims, while about a dozen others gathered at a neighborhood sheriff's station seeking news.
“I don’t have high hopes,” said a woman with four friends among the missing, declining to give her name. “We’ve just spent the night calling hospitals and listening to police scanners.
Parents and others shared contact information on a Facebook page and asked anyone with information about the missing to call. "ANY information please!" wrote a woman looking for her son.
Nine fatalities were initially confirmed, and authorities were "expecting the worst" as they sought to account for "a couple of dozen" people who were reported missing, Sergeant Ray Kelly, a spokesman for the county sheriff, told an afternoon news conference.
He later clarified that at least two dozen people remained unaccounted for Saturday night besides the nine victims whose remains were initially found and recovered from the rubble. Those bodies were transported to the coroner's bureau for identification.
He said an additional, unspecified number of bodies have since been spotted in the compromised structure but had not been reached.
Many of the victims were young people in their 20s or 30s, authorities said.
Drone aircraft equipped with thermal-imaging technology were sent inside the gutted structure looking for any signs of life, but none was found, Kelly said.
Deputy Fire Chief Mark Hoffmann said about a dozen people survived the blaze. Kelly said "several dozen" people who had been unaccounted for earlier had been found safe.
The dance party, featuring electronic music performances, took place on the second floor of the building, which had just two exits. A single makeshift staircase inside appeared to have been constructed from pallets.
The warehouse roof collapsed onto the second floor of the building during the fire, according to authorities, and portions of the second floor caved in on the first story.
Authorities said they did not suspect arson, but investigators want to find out if the building had a history of building code violations.
The city had received complaints about unpermitted construction at the building and opened an investigation, but an inspector failed to gain access to the structure in November and the inquiry remained open, according to the city's buildings and planning chief, Darin Ranelletti.
He said the city was aware of reports that people were living there, but no permits had been issued for habitation. It was unclear, he said, whether special permits would be needed for the artists who had set up shop inside.
Video footage posted on social media showed flames shooting from the structure, which was adorned with elaborate graffiti and colorful murals, as fire vehicles pumped plumes of water and heavy smoke engulfed the neighborhood.
Authorities have said they did not know how many people were at the party or how many lived on the premises.
But one eyewitness, who said he left the party to buy liquor and returned to find flames shooting from the second floor, said on Twitter that he saw about 60 to 70 people in the building.
"It was an inferno," Seung Y. Lee recounted in a post on his verified Twitter account.
Lee, who declined an interview, tweeted that the entire first floor was "covered in wood - antiques, furniture, etc. Beautiful but labyrinthine." He also described the wooden stairway as rickety and hazardous.
A Facebook event page showed 176 people planned to attend the party.
Ben Koss, an Oakland resident and musician, told Reuters he was on his way to the party with friends and arrived late to find smoke billowing from the warehouse moments before firefighters arrived.
"We tore down a fence so people could get out, but nobody came out," he said. "It was like a concrete kiln."
A few dozen mourners assembled Saturday night at the Church of the Chimes, about 7 miles (11 km) from the fire scene, to offer prayers for the dead and missing.