Four fire engines and around 25 firefighters were called to a small fire at a Metropolitan Police building on Wellington Way in Bow.
Part of a generator in a generator room was damaged by fire. There were no reports of any injuries.
The Brigade was called at 1908 and the fire was under control by 2003. Fire crews from Poplar, Whitechapel, Shadwell and Millwall fire stations attended the scene.
The cause of the fire is under investigation.