Firefighters evacuated the Forest Oak Towers, loading residents onto buses in the middle of the night.
Investigators said the fire heavily damaged 20 out of 180 apartments. About two dozen residents were displaced.
Authorities said the fire was set in a potted plant in a lobby on the building's ninth floor.
The fire triggered the building's sprinkler system and left a lot of water damage. Most people were allowed to return to their homes by Saturday evening.
Damage is estimated at $400,000.