More than 70 emergency calls were received by the control room from about 16:30 BST, and personnel from Mitcham, Wallington and Norbury stations were sent to the scene.
Passengers hoping to travel through Mitcham Junction should check the status of their trains as the railway remains affected by the fire and some services have been cancelled.
Road closures have also been put in place on London Road and Carshalton Road at the junctions of Willow Lane, Goat Road and Hackbridge Road.
Station Commander Jim Berry, who attended the scene, said: “Firefighters have worked hard this evening and have now brought this fire in Mitcham under control.
“Firefighting operations will continue overnight as crews fully extinguish the fire and dampen down hotspots, so please continue to avoid the area if you can.”
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