Firefighters working inside the burned warehouse on Sunday after the fatal fire in the Fruitvale district of Oakland, California.REUTERS/Lucy Nicholson

OAKLAND, California — Exhausted crews continued their search for more victims of a huge fire that tore through a converted warehouse in Oakland, California, during a dance party, with the toll of 36 known deaths expected to grow on Monday.

The cause of the blaze, which erupted late Friday in a two-story loft building that was home to an artist collective, has yet to be determined. It was the deadliest fire in the US in more than a decade.

As criminal investigators joined recovery efforts at the charred building, just east of San Francisco, firefighters have discovered the remains of nearly three dozen people as they picked through the debris-filled wreckage.

“We’re finding victims in every quadrant of the warehouse,” Sgt. Ray Kelly, the spokesman for the Alameda County Sheriff’s Office, said late Sunday. “We’re finding victims where we least expect them.”

Arson is not suspected, according to officials, but investigators are checking whether the building, which served as a base for the Ghost Ship Artists Collective and often hosted parties, had a history of code violations.

Mayor Libby Schaaf of Oakland said the Alameda County District Attorney’s Office had activated its criminal-investigation team and a representative of the prosecutor’s office was monitoring the recovery process. Schaaf said she was not authorized to say whether a criminal probe was underway.

The city’s first priority, the mayor said, was locating victims and supporting their relatives. “We have delivered the unacceptable and horrific news of losing a loved one to seven of our families,” Schaaf said.

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.

By Sunday evening, only 35% to 40% of the building had been searched, Kelly said. Officials are still unsure how many people were inside at the time.

Chris Nechodom, 30, said he was on the ground floor when he saw flames race across the ceiling. As he fled, he heard a loud noise and saw a plume of thick black smoke.

“It blew out maybe 10 feet out of the entrance,” Nechodom said. “After that, I saw a few more people crawl out.”

Some teenage victims

A woman praying at the makeshift memorial near the scene of the fatal warehouse fire in Oakland.REUTERS/Stephen Lam

The building had been designated for use as a warehouse only, according to city officials, who were aware of reports that people were living there, though no permits had been issued.

The recovery operation was delayed as the roof collapsed and the second story fell onto the first. The effort has proceeded slowly because of the mountains of debris.

With many of the victims burned beyond recognition, families have been asked to preserve items that might contain their DNA to help identification.

After notifying the families, the Alameda County coroner released the names of seven victims, all from California, who had been positively identified.

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

A mourner looking at the makeshift memorial near the scene of a fatal warehouse fire in Oakland. REUTERS/Stephen Lam

It was the deadliest blaze in the US since 100 people perished in a 2003 fire at a Rhode Island nightclub.

Exhaustion has been taking an emotional toll on fire crews who have worked around the clock. One of those killed was the son of a sheriff’s deputy, Kelly said.

“This tragedy has hit very close to home,” he said.

Online photos of the warehouse from before the blaze showed it filled with an array of musical instruments, statues, and antiques. Furnished with big sofas and colorful carpets, it featured a maze of side rooms and nooks.

“The whole place was built like you are going to set up for a fire,” said Matt Hummel, 46, who twice visited before the fire and has helped renovate other warehouse spaces for artists.

(Additional reporting by Tim McLaughlin in Chicago and Sharon Bernstein in Sacramento, Calif; Writing by Daniel Wallis; Editing by Jeffrey Benkoe)