A man was sent to hospital with burns on his hands following a fire in a garage being used as a temporary bedroom.
Firefighters were called to the blaze in Lower Richmond Road, Putney, just after 3am on Saturday morning.
They were alerted to it after a group of people coming back from a nightclub in fancy dress spotted smoke.
It was put out by 5am and believed to have been caused by a candle.
The man sleeping in the garage was sent to Charing Cross hospital with burns on his hands and smoke inhalation.
A spokesperson for the fire brigade praised the youngsters who alerted them to the fire.
He said: "If it hadn't have been for them it could have been depressing."
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