The origin of the blaze, which erupted late on Friday in a two-story structure that occupied half a city block and housed an artists' collective, has yet to be determined.

It ranks as the deadliest fire in the United States in more than a decade.

Authorities have said arson was not immediately suspected. But a team of criminal investigators from the Alameda County District Attorney's Office has been activated, and prosecutors are monitoring the recovery process, Oakland Mayor Libby Schaaf said on Sunday.

The nature of the fire has raised questions about whether building code violations might have been a factor.

City officials have said the warehouse, known locally as the Ghost Ship, was under investigation for complaints of illegal construction inside.

Municipal authorities also cited reports that people were living in the structure even though it was not permitted for residential use.

A number of individuals who had been inside the warehouse described it as a potential fire trap.

The first floor of the building, which housed a group of artists who called themselves the Satya Yuga Collective, was a cluttered warren of partitioned studio spaces and rooms crammed with furniture, musical instruments, antiques, sculptures, wall-hangings and rugs, according to photos posted on social media before the fire and accounts of survivors and city officials.

The dance party was held on the second floor, which partially collapsed when the roof gave way in the fire.

There was no evidence of sprinklers or smoke detectors, and a makeshift stairway between the first and second floors was at least partly constructed from wooden pallets, Oakland Fire Chief Teresa Deloach Reed has said.

City officials said the building had just two exits.

The recovery of three more bodies from the charred ruins brought the official tally of dead to three dozen.

Search crews suspended work in the early hours of Monday due to a wobbly exterior wall.

About 70 percent of the site had been searched at that point, authorities said.

The mayor said work resumed later in the morning after the wreckage was further stabilized.

The city's first priority, Schaaf said, was locating victims and supporting their relatives. As of Monday morning, 11 of the dead had been identified, police said.

Some of the victims were 17 or younger, although most were in their 20s and 30s, officials said. Some were from elsewhere in the country and abroad.

With many burned beyond recognition, families were asked to preserve items that might contain their DNA to help identification.

Officials are still unsure how many people were inside when the blaze broke out.

One survivor has estimated there were 60 to 70 in the building at the time.

The warehouse was one of many converted lofts in Oakland's Fruitvale neighborhood, a mostly Latino district where rents are generally lower than in the rest of city.

S/SH 11