Four fire engines and around 25 firefighters were called to a fire at a mixed-used commercial building at the rear of a restaurant on Ridley Road in Hackney.
A shed on the flat roof of a single-storey building was destroyed by the fire and part of the roof was also damaged. There were no reports of any injuries.
The Brigade's fire investigators believe the fire was caused by the unsafe disposal of smoking materials.
A London Fire Brigade spokesperson said: "If you are a smoker, it's absolutely vital you ensure your cigarette is completely out when you've finished smoking it.
"Make sure smoking materials are cold before emptying ashtrays. Preferably wet stubs before them into a bin."
The Brigade's 999 Control Officers took 30 calls to the blaze.
The Brigade was called at 2244 and the fire was under control by 2353. Fire crews from Stoke Newington and Homerton fire stations were at the scene.