Six fire engines and around 40 firefighters were called to a fire at a disused gas works site on Homesdale Road in Bromley.
A decommissioned gas holder was destroyed by the fire.
A 50 metre cordon was in place while firefighters tackled the fire and residents in the immediate were advised to keep their windows and doors closed due to the smoke.
There were no reports of any injuries.
The Brigade's 999 Control Officers took around 70 calls to the fire.
Around 150 residents and a nearby school were evacuated as a precaution.
The Brigade was called at 1131 and the fire was under control by 1449, but crews will remain on scene damping down throughout the afternoon. Fire crews from Bromley, Sidcup and Orpington fire stations attended.
The cause of the fire is accidental and believed to be due to hot gas works being carried out.