Firefighters were called to reports of a ruptured gas main on Mitcham Road in Croydon.
A number of people were evacuated from nearby properties and a 130m cordon was put in place as a precaution.
Part of Mitcham Road was closed from Moys Close.
Crews supported emergency services colleagues and gas engineers who worked to isolate supplies.
The gas main was repaired by Southern Gas Networks and there were no further elevated gas readings.
The Brigade was called at 1201 and the incident was over for firefighters by 2307.