Firefighters were called to a gas leak at a derelict house on Dudden Hill Lane in Willesden.
A 50-metre cordon was put in place and around 100 people were evacuated from neighbouring properties as a precaution after high levels of gas were detected. There were no reports of any injuries.
Firefighters carried out a sweep of the surrounding area to check for elevated readings of gas and confirmed no elevated readings remained.
The Brigade was called at 1624 and the incident was over for firefighters by 2034. Two fire engines from Willesden and West Hampstead fire stations and three fire rescue units from Bethnal Green, Homerton and Wembley fire stations attended the scene.