The fire at a multi-story apartment building in the 900 block of O'Farrell Street between Van Ness Avenue and Polk Street was reported around 11:10 a.m., the dispatcher said.
The blaze was under control shortly after noon, according to the dispatcher.
The American Red Cross was called to assist 12 adults displaced by the fire, the dispatcher said.
Emergency crews treated and released people at the scene however the dispatcher did not have information on injuries.
The cause of the fire is under investigation.