Six fire engines and 35 firefighters and officers were called to a fire at a commercial building in Westferry Circus in Canary Wharf.
Part of a plant room on the ninth floor of the building was damaged by fire.
The Brigade was called at 0615 and the fire was under control at 0800. Fire crews from Millwall, Poplar, Shadwell, Whitechapel, Bethnal Green and Dowgate fire stations attended the scene.
The cause of the fire is under investigation.