At around 11:15 p.m., units responded to fire that was initially reported in a building in the 500 block of Columbus Street, San Francisco fire Lt. Ken Smith said.
Firefighters arrived within minutes, Smith said, but discovered the fire was actually burning in a unit located behind a three-story building of residential flats in the 600 block of Green Street, also called Beach Blanket Babylon Boulevard because of a variety show performed in a theater on that block.
"The guys did an excellent job of locating the fire," Smith said.
More than 95 fire personnel ultimately responded to the blaze, which escalated to a third alarm at about 11:30 p.m., Smith said, and was successfully kept from spreading to nearby structures.
Before the fire was declared under control at around 12:15 a.m., four units had sustained significant damage, Smith said, and a neighboring building was slightly damaged.
No injuries were reported, Smith said, though seven residents were displaced and getting help from the American Red Cross to secure temporary housing.
The cause of the fire was under investigation.