Eight fire engines and around 60 firefighters were called to a fire in a block of flats on River Gardens Walk, Greenwich.
Part of a balcony and a flat on the 10th floor were damaged by fire. Two women left the flat before crews arrived. There were no reports of any injuries.
The fire is believed to have been accidental and caused by the unsafe disposal of smoking materials on a roof terrace.
A London Fire Brigade spokesperson said: “We’d rather you didn’t smoke at all, but if you are a smoker, it’s absolutely vital you ensure your cigarette is completely out when you’ve finished smoking it.
“Always empty ashtrays carefully. Make sure smoking materials are out, cold and preferably wet them before throwing them into a bin. If you don’t, you risk causing a fire.”
The Brigade was called at 0805 and the fire was under control by 0913. Fire crews from Deptford, New Cross, Poplar, Peckham and surrounding stations were at the scene.