Eight fire engines and around 60 firefighters dealt with a fire at a supermarket on Tollgate Road in Beckton.
Part of the roof was damaged by the blaze.
The Brigade was called at 0405 and the fire was under control by 0700. Fire crews from East Ham, Plaistow, Barking, Poplar, Ilford, Homerton, Stratford and Millwall fire stations are at the scene. The cause of the fire is under investigation.