Fire fighters have attended 13 grass fires on Mitcham Common in just two days.
Crews from Mitcham and Norbury were called out five times on Sunday, August 4, to reports of grass fires at Mitcham Common, and a further eight times yesterday.
The largest fire affected a 300m square area, about the size of two to three football pitches.
All of the fires involved grass, shrub or trees being alight and were described as secondary fires which were put out in minutes.
The cause of the fires has not been established but could have been through people's carelessness when disposing of cigarettes.
Deliberate acts of arson have not been ruled out and police are investigating.
A spokesman for the fire brigade said: "We would like to remind people that if they are out walking please dispose of your cigarette carefully.
"It’s so dry out there despite the rain."
Last month a fire the size of four football pitches broke out on the Common, destroying four hectares of land.
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