Ten fire engines and around 70 firefighters were called to the blaze on Brunel Street in Newham.
Firefighters tackled flames within a three roomed flat on the second floor of an eleven-storey building currently under construction.
A significant part of the flat was damaged by the fire, no injuries were reported.
Around 200 construction workers left the building and another 400 workers left surrounding construction sites before the Brigade arrived.
Vistry Partnerships is main contractor on the £250m development.