Twelve fire engines and around 80 firefighters were called to a fire at an industrial estate on Kemp Road in Dagenham.
A range of single-storey industrial units and three cars were destroyed by the blaze and a further unit was damaged. There were no reports of any injuries.
Station Commander Paul Green, who was at the scene, said: "Firefighters tackled a significant fire involving a number of industrial units.
"Nearby residents were advised to keep their doors and windows closed while crews worked to extinguish the blaze as there was heavy smoke in the area."
The Brigade's 999 Control Officers took more than 50 calls to the fire.
The Brigade was called at 1914 and the fire was under control by 2148. Fire crews from Barking, Dagenham, Hainault, Ilford, Romford, Tottenham and surrounding fire stations were at the scene.
The cause of the fire is under investigation.