Eight fire engines and around 60 firefighters were called to a fire at a storage depot on Hertford Road in Barking.
The ground floor of a four-storey self-storage unit was damaged by the fire. There were no reports of any injuries.
Station Commander Paul Easton, who was at the scene, said: "A member of staff discovered the fire after noticing smoke coming from a storage unit and they immediately called 999.
"Fortunately all the staff who were in the building were able to get out and there were no reports of any injuries.
"Firefighters wearing breathing apparatus extinguished the fire and then used breaking in gear to force entry into neighbouring units to prevent any further fire spread."
The Brigade was called at 1828 and the fire was under control by 1934. Fire crews from East Ham, Barking, Plaistow, Ilford and Stratford fire stations were at the scene.
The cause of the fire is believed to have been the failure of a lithium-ion battery.