Four fire engines and around 25 firefighters were called to a fire at a house converted into flats on Dulwich Road in Herne Hill.
Part of a flat on the upper ground floor and part of a flat on the first floor were damaged by the fire. Two people left the building before the Brigade arrived. There were no reports of any injuries.
The fire was discovered after a resident heard a bang and saw smoke. They left the building and called the Brigade.
The Brigade was called at 1600 and the fire was under control by 1832. Fire crews from Brixton, Clapham, West Norwood and Peckham fire stations were at the scene.
The fire is believed to have been electrical.