Four fire engines and around 25 firefighters were called to a fire at a nursery under refurbishment on The Green in Wanstead.
A small part of the basement was damaged by the fire. There were no reports of any injuries.
The Brigade was called at 1045 and the fire was under control by 1118. Fire crews from Leytonstone, Stratford, Woodford and Leyton fire stations were at the scene.
The Brigade's Fire Investigators believe the fire was caused by an incandescent lightbulb coming into contact with a dust sheet, which caught alight.