The fire was reported at 4:39 a.m. in the 2100 block of Bancroft Avenue near San Leandro High School, according to fire officials.
About 50 residents were evacuated from the property and one person was reportedly injured. The extent of their injuries has not been released, fire officials said.
The American Red Cross is responding to assist the temporarily displaced residents Thursday morning.
The fire was knocked down at about 5:30 a.m., according to fire officials.
Fire investigators are looking into the cause of fire.