Five fire engines and around 35 firefighters were called to a fire at a block of flats on St Gabriel Walk in Elephant and Castle.
Part of the external balcony of a flat on the 21st floor of a 35-storey block was damaged by the fire. Around 200 people left the building before the Brigade arrived. There were no reports of any injuries.
Station Commander Jon Singleton, who was at the scene, said: "There were a lot of items stored on the balcony which contributed to the severity of the blaze.
"Fortunately, the swift action and hard work of crews prevented the fire from spreading inside the property.
"There is some safety advice you can follow to avoid balcony fires, including never storing combustible items on your balcony as they can catch light and contribute to fires spreading.
"We also advise that if you are smoking on your balcony, always ensure your cigarette is properly out and never throw it over the side as it could catch light to possessions on balconies below or next to yours."
The Brigade was called at 1016 and the fire was under control by 1115. Fire crews from Lambeth, Old Kent Road, Dowgate and Dockhead fire stations were at the scene.
The Brigade's fire investigators believe the fire was accidental and caused by the unsafe disposal of smoking materials.
Safety advice for smokers:
• It's safer to smoke outside, but make sure cigarettes are put right out and disposed of properly.
• Never smoke in bed, and avoid smoking on arm chairs and sofas – especially if you think you might fall asleep.
• Take extra care when you’re tired, taking prescription drugs or if you’ve been drinking alcohol.
• Use proper ashtrays, which can’t tip over and stub cigarettes out properly.
• Don't balance cigars or cigarettes on the edge of an ashtray, or anything else – they can tip and fall as they burn away and cause a fire.
• Don’t leave lit pipes or cigarettes unattended.
• Always empty ashtrays carefully. Make sure smoking materials are out, cold and preferably wet them before throwing into a bin – never use a wastepaper basket.
• Keep matches and lighters out of children’s reach, and buy child resistant lighters.
• Never smoke if you use healthcare equipment like medical oxygen, an air flow pressure relief mattress or emollient creams.
• Consider additional safety measures such as fire retardant bedding or nightwear.