A blaze in a three-storey converted house was caused by a lit cigarette not properly put out, according to London Fire Brigade (LFB).
Four fire engines and around 25 firefighters were called just after midnight on Thursday (September 14) to a fire in Digby Crescent in Stoke Newington.
Most of a first-floor flat, inside a three-storey house converted into flats, was damaged by flames, LFB said.
The brigade's 999 control officers received 12 calls about the fire.
One man left the flat before firefighters arrived and was treated at the scene by London Ambulance Service crews.
Crews from Stoke Newington, Holloway and Islington fire stations had the blaze under control by 1.32am.
The fire was caused by the unsafe disposal of smoking materials.
An LFB spokesperson added: "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.
"If you don't, you risk causing a fire which could not only destroy properties but also cost you your life."
Firefighters advised smokers to always use proper ashtrays which cannot tip over and not to leave lit pipes or cigarettes unattended.
The spokesperson said people should always empty ashtrays carefully making sure smoking materials are out, cold and preferably wet them before throwing into a bin – never use a wastepaper basket.
They said it is safer to smoke outside, but if not to make sure cigarettes are put right out and disposed of properly.
Balancing cigars or cigarettes on the edge of an ashtray or anything else can tip and fall as they burn away and cause a fire, they added.
The spokesperson said smokers should take extra care when tired, taking prescription drugs or if they've been drinking alcohol.
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