Firefighters feared an explosion after suspected arsonists set fire to a bin store near gas meters in Carshalton last night.
A crew from Wallington fire station was called out to the storage area off Beacon Grove at 9pm.
Rubbish inside a small brick building had been set on fire close to several gas meters.
Neighbours told firefighters they thought gas cylinders were nearby.
The firefighters were able to put the fire out before the flames reached the gas meters and then made the area safe.
The incident has been reported to police.
Firefighters from Sutton fire station were called to reports of smoke in Whitby Road at 11.30pm.
The smoke turned out to be coming from a bonfire and firefighters took no further action.
A spokesman said it is still safest to call 999 if you have any suspicions about a fire, even if it does turn out to be a bonfire.