Thirteen people were injured at a building under construction in the Pill Hill area that partially collapsed Friday, authorities said.
Some were taken to hospitals and no fatalities or major injuries have been reported, Oakland police said.
Workers were in the process of pouring concrete on the second floor when the collapse happened, officials said.
Some were caught in the concrete and others hung from scaffolding. Some workers were able to get to safety on their own and others were assisted by firefighters.
Footage from a news helicopter showed firefighters tending to at least three workers, two of whom were strapped to stretchers.