Four fire engines and around 25 firefighters were called to a fire at a house converted into flats on Northumberland Park in Erith.
Part of the staircase from the ground to the first floor of the building was damaged by fire. There were no reports of any injuries.
A London Fire Brigade spokesperson said: "On arrival, crews found the communal staircase alight between the ground and first floor.
"Firefighters wearing breathing apparatus carried out a search of the property and found no one inside the building."
The Brigade was called at 1521 and the fire was under control by 1610. Fire crews from Bexley, Erith and Plumstead fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.