Residents in Colindale were forced to flee their homes and two were taken to hospital after a cigarette started a fire in their block of flats.
The blaze broke out in the flats in Aerodrome Road, resulting in two people being treated for smoke inhalation and 37 residents being evacuated by fire fighters on Saturday just after 9.30pm.
Another two residents left their home before fir crews arrived.
Six fire engines and 35 firefighters and officers from Mill Hill, Finchley and Stanmore fire stations fought the blaze for two hours.
A spokesman for the London Fire Brigade has urged smokers to ensure they stub their cigarettes are out properly.
He added: If you don’t, you risk causing a fire that could destroy not only your home, but also your life.”
“Fires caused by smoking materials - including cigarettes, roll-ups, cigars and pipe tobacco - result in more deaths than any other type of fire. Last year around three fires a day in London were linked to smoking and half of accidental fire deaths were related to careless disposal of cigarettes.”
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