"When we started this investigation, if you would have told us we would have 33 victims, we wouldn't have believed you," Sergeant Ray Kelly of the Alameda County Sheriff's Department told reporters, adding that crews had searched less than half of the gutted building.
"I don't know how many people are left in there. We have no idea how many people were in that building that night... We're expecting the worst and hoping for the best in regards to how many more victims we find."
The fire in Oakland, near San Francisco, broke out about 11:30 pm Friday (0730 GMT Saturday) at the cluttered warehouse where artists and students worked and lived, even though the structure wasn't licensed for such use.
The electronic dance music party, with between 50 and 100 guests, also took place without a permit. Although the cause of the fast-moving blaze remains under investigation, Oakland Mayor Libby Schaaf said the district attorney had opened a criminal investigation as a precaution to preserve options as the case unfolds.
"You have to understand that the scope of this tragedy is tremendous," she said. "We have many, many witnesses to interview. We are in the process of doing that."
Eight victims have been identified based on fingerprints so far, ranging in age from 17 to 35. Some were from Europe and Asia, and the Oakland authorities are working with the State Department to contact foreign governments, Kelly said, declining to reveal which countries.
Bodies were found scattered throughout the warehouse, known locally as Oakland Ghost Ship. "We're finding people throughout the entire square footage of that structure," Kelly said. "It's so random. We're finding victims where we least expect it."
The authorities yesterday asked relatives of the missing to "eliminate future delays" in identifying victims by preserving such items as hairbrushes and toothbrushes for DNA samples.
"We will ask for them as we need them," said Captain Melanie Ditzenberger of the sheriff's department coroner's bureau. Oakland Fire Chief Teresa Deloach Reed has said the interior of the warehouse was maze-like, "filled end-to-end with furniture, whatnot, collections."
"There wasn't a real entry or exit path," she said. Images published online show artwork, pianos and wooden objects throughout the building, which helps explain why the blaze raced through the structure despite firefighters' arrival within three minutes.