Five fire engines and around 35 firefighters tackled a flat fire on Thurston Road in Lewisham.
Part of a four-roomed flat on the second floor of a residential block was damaged by fire. Around 50 people were out of the building before the Brigade arrived. One person was assessed on scene by London Ambulance Service crews.
The fire is believed to have been accidental and caused by smoking materials.
A London Fire Brigade spokesperson said: “Fires caused by smoking materials including cigarettes, roll-ups, cigars and pipes, result in more deaths than any other type of fire.
“Never leave lit cigarettes unattended and make sure to stub them out properly and dispose of them carefully when you have finished smoking.
“If you don’t you risk causing a fire, which could not only destroy your home, but also put lives at risk.”
The Brigade was called at 1447 and the fire was under control by 1612. Fire crews from Lewisham, Deptford, New Cross, Orpington and Forest Hill fire stations attended the scene.