Eight fire engines and around 60 firefighters are tackling a blaze at an industrial estate on Hainault Road in Romford.
A single industrial unit of two floors is alight. There are no reports of any injuries.
The Brigade was called at just before 9pm on Wednesday evening.
Crew Commanders took the steps in the earlier stage of the operation to manage the fire in three sectors.
A specialist aerial ladder has also been brought in to assist with tackle the fire.
A number of hose reels are in uses along with two command unit that have been sent to the incident.
Safety officers and investigators from the London Fire brigade arson task force have also been sent to the incident to help discover the cause of the blaze.