Four fire engines and 21 firefighters and officers were called to a fire in a basement in Dulwich Road, Herme Hill.
A motor in a plant room was burnt out.
Approximately 40 people were evacuated before the arrival of the Brigade. There were no reports of any injuries.
The Brigade was called at 0344 and the incident was over at 0417. Fire crews from Brixton, West Norwood and Clapham fire stations attended the scene.
The cause of the fire is believed to be accidental.