Eight fire engines and around 60 firefighters tackled the blaze on New Road in Rainham.
Firefighters were called just before 5pm and the blaze was under control by 8pm.
Two dogs died at the scene. No humans were hurt.
A single-storey car workshop and a further car workshop with a mezzanine floor were both destroyed by fire. Seven cars were also destroyed by the blaze.
Firefighters removed 12 gas cylinders as a precautionary measure.
Station Commander Neil Guyett said: "The whole of a single storey car workshop was damaged by fire. Firefighters remained at the scene throughout the night damping down small pockets of fire."
The Brigade’s 999 Control Officers took 13 calls to the blaze.
Fire crews from Wennington, Dagenham, Barking, Hornchurch and Ilford fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.
