Firefighters were forced to break into a bookmakers when fire broke out.
They were called to Paddy Power, in Tooting High Street, Tooting, at 4am this morning.
The blaze started in the front door of the shop and is believed to have been caused by a discarded cigarette.
Fire crews left the scene at about 7am, with three fire engines needed to put it out.
No people were involved.
The front of the shop has been left damaged.
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