Four fire engines and around 25 firefighters responded to a fire on Balham New Road, Balham.
The fire was located in the basement of a commercial property, which was partially damaged as a result of the fire. Five people were evacuated from an adjacent property as a precaution whilst crews responded.
The Brigade was first called about the incident at 0249, and crews from Tooting, Clapham and Battersea fire stations were sent to the scene. Firefighters had the incident under control by 0552.
The fire is believed to have been accidental, caused by a fault in an extractor fan.