Ten fire engines and around 70 firefighters tackled a fire at a range of shops with flats above in Longbridge Road, Barking.
Part of a restaurant on the ground floor and part of a flat on the first floor were alight. There are no reports of injuries at this stage.
Longbridge Road was closed from Fanshaw roundabout to Salisbury Avenue.
Station Commander Steven Vydelingum, who was at the scene, said: "Crews are working hard to bring this fire under control. Due to the road closure in place there is congestion in the area and motorists are advised to avoid the area if possible."
The Brigade was called at 1924 and the fire was under control by 2057. Fire crews from Barking, Ilford, East Ham, Plaistow and surrounding stations were at the scene.
The cause of the fire is under investigation.