OAKLAND, Calif. (AP) — San Francisco Bay Area authorities say a fire has broken out at an Oakland warehouse where people were having a party, and police say there are "casualties."

Oakland police Officer G. Plasencia says the fire department responded about 11:30 p.m. Friday and that firefighters were still on the scene early Saturday morning. Oakland firefighters tweeted video of the fire erupting through the roof.

Authorities told KTVU-TV about 50 people were inside the building, which houses a group of artists and their studios.

Plasencia said he had no further description of the casualties and referred an Associated Press reporter to the coroner's office. The office said the coroners were also at the scene Saturday morning and unavailable for comment. The fire department also had no immediate details.