OAKLAND, CALIF. - One of the deadliest fires in recent U.S. history began amid a cluttered collective of artist studios known as the Ghost Ship and spread quickly through the two-story warehouse that did not have fire sprinklers, killing at least 33 people and possibly many more, officials said Sunday.

"Help me!" shouted partygoers who had gathered at the warehouse for a Friday evening of music and dancing in East Oakland's Fruitvale district, only to find themselves trapped in an inferno.

Fire trucks arrived within three minutes, officials said, but nothing could be done to stop the fast-spreading flames soon enough. The sky was lit with a huge fireball, ignited by an array of artisan works, guitars, pianos, bookshelves, bowls, and countless other tinderlike pieces.

Bob Mule, a photographer who worked at the warehouse, told the local NBC-TV station that he saw the fire coming from the back left corner of the building. He heard a friend with a broken ankle calling for help. Mule said he raced to the friend, but "there was a lot of stuff in the way and the flames were too much. ... I had to let him go."

Standing outside the warehouse as flames continued to pour through the walls and the roof, with an arm bandaged from wounds suffered during his flight from the fire, Mule said he had not heard whether his friend had made it out.

As the fire raged, city officials met with roomful of families who had undertaken anguished searches for relatives. The rescue effort quickly turned into a salvage operation. By midafternoon Sunday, officials had searched about 35 percent of the building and discovered 33 bodies, many of them charred beyond recognition, and expected to find many more. One survivor estimated that at least 50 people had been in the building. The youngest victim identified as of Sunday afternoon was 17.

Firefighters moved slowly in the search, walking amid fallen beams and smoldering ruins looking for bodies. They undertook their mission at great risk, with ceilings and floors in danger of collapse. They doused flames by passing buckets down the line. The firefighters ranged in experience from a few months to 30 years, but all were affected by the intensity of the blaze and the piles of bodies they encountered along the way, officials said.

The warehouse had long been the subject of complaints. Local officials said they had been alerted to possible code violations on Nov. 13, but they could not get inside the structure when they visited four days later. Local news outlets reported that a number of artists had used the building as their sleeping quarters as well as studios.

Asked on Sunday about the inspection, Oakland Mayor Libby Schaaf said: "The complaint alleged there was blight and external trash and debris, not just around the building but in the adjacent lot that is owned by the same owner. They also alleged there was illegal or unpermitted construction inside, and possible residential use. ... The inspector was able to document the external blight but was unable to gain access to the building. So that investigation had remained open and an initial notice of violation was issued to the owner with regard to the blight."

Local officials said it was the deadliest fire they could recall in the city, and it ranked as one of the worst structural fires in recent national history. The deadliest fire in recent years occurred in 2003, when 100 people died at a Rhode Island nightclub called the Station.

The fire began around 11:30 p.m. Friday, as partygoers gathered on the second floor to listen to a music group called Golden Donna. The band played before a dance floor of about 2,500 square feet inside the roughly 10,000-square-foot warehouse.

By the time firefighters arrived at the scene, the staircase had burned away, Mark Hoffmann, deputy chief of the Oakland Fire Department, said Saturday.

Firefighters used special equipment to breach a wall and then deployed the most basic means to carefully make their way inside, clearing debris with shovels and other hand tools, and dousing flames with buckets passed from one person to another.

"We had firefighters with basically coveralls and buckets and shovels, taking bits of debris out into the vacant lot, to be then loaded into dump trucks and removed to an off-site location," Melinda Drayton of the Oakland Fire Department said at a news conference near the scene. "This will be a long and arduous process, but we want to make sure we are respecting the victims, their families and our firefighters' safety to work slowly and carefully through the building."

Drayton said she was inside the structure and watched "the somber approach that [firefighters] took to this search. It was quiet, it was heartbreaking."

She said crews found 10 of the victims in the middle of the building. Four of them were close together, and the other six were within 10 feet. Three more were found on the east side of the building, Drayton said.

Sgt. Ray Kelly, spokesman for the Alameda County Sheriff's Office, said the death toll will go up. "We will be here for days and days to come," Kelly said. "We anticipate that the number of victims will rise and will increase."

Questions remain about whether electrical issues, pyrotechnics or errant candles or cigarettes had started the fire. Fire officials said the building did not have sprinklers. A criminal investigation team was sent to the site to preserve the option of a possible prosecution.

The music event's Facebook page was filled with inquiries from people looking for their loved ones or offering assistance to families and friends of the victims.