Authorities have recovered 33 bodies in a fire that razed a converted warehouse on a Friday night concert and expected to find more. Identified victims were local artists and teenagers as young as 17 years old.

It is considered as one of the deadliest fire structure incidents in the United States since the Feb. 2003 fire accident at a nightclub in Warwick, Rhode Island.The victims were believed to have been asphyxiated by the fumes which continued for several hours.

Authorities have declared on Sunday they opened a criminal investigation despite stating arson was ruled out earlier. The warehouse is known as the "Ghost Ship" and was blazed around 11:30 p.m. on Friday night.

The warehouse serves as a function for parties and an installation art studio. Though the firefighters have successfully put out the fire on Saturday, the building is still considered unsafe for emergency response teams to venture.

Mark Hoffman, Oakland Fire Department Deputy, said in a press briefing that "the roof of the building collapsed, onto the second floor, which also in many areas collapsedg onto the first floor, further complicating our ability to continue the recovery effort."

Oakland Fire Chief Teresa Reed stated: "We have a lot more to go, we're going to be here for a few more days, just getting through the building, if you do the math." Officials and the fire-fighting team said they have just scouted not more than 30 percent of the building yet.

Families of the victims and other survivors watched firefighters putting out the flames while waiting for their sons and daughters walk out alive. About 50 to 100 people attended the event. California Gov. Jerry Brown took to Twitter to express his sympathies, "Our thoughts are with the entire city in this difficult time & we extend our condolences to the family & friends of those lost."