Four fire engines and around 25 firefighters tackled a fire at a house converted into flats on Cedar Road in Sutton.
Part of a flat on the second floor of the building was damaged by fire. A woman and child had left the flat before crews arrived. There were no reports of any injuries.
The fire is believed to have been accidental and involved a tumble dryer.
A London Fire Brigade spokesperson said: “It’s important to make sure you’re aware of white goods safety and to check your appliances.
“If your white goods start making a strange noise, don’t ignore it. If you think there’s a problem always unplug it and contact the manufacturer or a qualified repair technician.
“Most fires where white goods are the source of ignition are not down to anything you have done – so always make sure you register your appliances as you’ll be informed if any issues are identified with the product you’ve bought.
“You should also always keep your white goods in a safe place out of the way as if a fire does break out you will need clear escape routes."
The Brigade was called at 1141 and the fire was under control by 1310. Crews from Sutton, Wallington and Croydon fire stations attended the scene.