Four fire engines and around 25 firefighters were called to a fire at a care home on Central Way in Thamesmead.
Part of a three-roomed flat on the second floor was damaged by the fire. Crews evacuated around 20 residents and 10 staff as a precaution. There were no reports of any injuries.
The Brigade was called at 1400 and the fire was under control by 1518. Fire crews from Plumstead, Erith and East Greenwich fire stations attended the scene.
The Brigade’s fire investigators believe the fire was accidental and started in a filtration system in a fish tank.