Twenty fire engines and around 125 firefighters were called to a fire at an industrial estate on Alfreds Way in Barking.
A single-storey builders' merchant warehouse was destroyed by the fire and part of an adjoining warehouse was also damaged. There were no reports of any injuries.
The Brigade's 999 Control Officers took 80 calls to the blaze.
Station Manager Jim Smith, who was at the scene, said: "On arrival crews were faced with a well developed fire and large clouds of smoke.
"Crews worked hard to prevent the fire spreading to mezzanine offices."
The Brigade was called at 1833 and the fire was under control by 0057 (Saturday). Fire crews from Barking, East Ham, Dagenham, Plaistow, Ilford and surrounding fire stations were at the scene.
The cause of the fire is under investigation.