OAKLAND: At least nine people were killed and dozens missing after fire raced through a warehouse dance party in Oakland, California, authorities said on Saturday, adding they feared the death toll would rise once search teams entered the gutted building.

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 pm 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 shored up and recovery crews were able to safely move into the structures 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."

Anguished friends of the missing huddled at a nearby pub waiting for word on their fate, 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.

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.

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.

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.

The remains of just one of the nine confirmed dead had been recovered as of Saturday because the warehouse was still too unstable to enter, said Deputy Fire Chief Mark Hoffmann.

He said about a dozen people survived the blaze, including one who went to a local hospital for treatment.

The party was taking place on the second floor of the building, which had just two exits, one for each floor. A single makeshift staircase appeared to be constructed from pallets. The fire chief said there were no indication of any smoke detectors in the building.

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.

ILLEGAL CONSTRUCTION?

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 on Nov. 7, 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.

Many of the victims were young people in their 20s or 30s, authorities said.

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.

'LIKE A CONCRETE KILN'

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, which featured electronic music performances.

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."

Parents and others shared contact information on the page and asked anyone with information about the missing to call. "ANY information please!" wrote a woman looking for her son.