Smoke pours from a warehouse, which caught fire during a dance party in Oakland, California, Dec. 3, 2016. SEUNG LEE/HANDOUT VIA REUTERS

UPDATE: 6:25 p.m. EST — Officials late Sunday raised the death toll to 33.

Oakland Mayor Libby Schaaf announced a criminal investigation would begin.

UPDATE: 10:30 a.m. EST — Officials Sunday raised the death toll in the Oakland Ghost Ship Warehouse fire to 24 following an all-night search of the burned-out building. Sheriff’s Sgt. Ray Kelly told an early morning news conference 15 bodies were pulled from the wreckage overnight, added to the nine victims found in the immediate aftermath. So far, 20 percent of the building has been searched, Fire Battalion Chief Melinda Drayton said. The families of seven of the 24 victims have been notified, Drayton said.

Original story

The death toll in the Oakland warehouse fire, which broke out Friday night during a party, could rise to at least 40, officials said Saturday. Nine people were confirmed dead but dozens are still missing. Most victims are believed to be young and some were foreigners.

“We’re expecting the worst — maybe a couple dozen victims here,” Sgt. Ray Kelly, spokesman for the Alameda County Sheriff’s Office, reportedly said Saturday. “We did not have a lot of victims go to the hospital. It appears that people either made it out, or they didn’t make it out.”

He added that another two dozen people who were believed to be missing have been located. The fire broke out Friday night during a concert on the second floor of the warehouse called the Oakland Ghost Ship.

Oakland Fire Chief Teresa Deloach-Reed told the Washington Post over 50 people were inside the building, which was used as studio space for an art collective and parties. The building was not equipped with sprinklers.

However, city records revealed allegations of at least three code violations at the warehouse in 2016. “This property is a storage [facility], but the owner turned it into a trash recycling center. The yard became a trash collection site, and the main building was [remodeled] for residential,” the records reportedly showed.

City officials also said Saturday afternoon that the building was permitted for use as a warehouse but not for dwelling. However, witnesses said some artists lived in the building. The party would have also required a legal permit given the building’s zoning, but did not have one.

The building’s roof caved in during the fire, making it too unstable to enter, according to Oakland Fire Department’s deputy chief Mark Hoffmann. Kelly said it would take about two days to complete the search for victims possibly trapped under the debris.

Officials used drones equipped with thermal technology to locate survivors. “The drones were being used with a thermal imager,” Kelly said. “It’s very, very helpful technology. It allows us to focus in, and we can actually see the heat coming off of someone if they are alive. We didn’t see any heat signatures of live people. Not to say that there’s not, but the chances are very small.”

He added: “This is just a tragedy, and there are no easy answers. This is not an easy task.”

Officials were still investigating the cause for the fire. While arson was not suspected, investigators said they had not ruled out any possibility.

Oakland Mayor Libby Schaaf said in a statement Saturday: “Last night’s fire was an immense tragedy. I am grateful for our first responders for their efforts to deal with this deadly fire. Our focus right now is on the victims and their families and ensuring that we have a full accounting for everyone who was impacted by this tragedy.”