The Canary Wharf Group said the fire started on a “non-essential” part of the site and was extinguished quickly with no casualties.
It added that “the safety of individuals on the Estate remains our highest priority.”
The fire struck at a site on Preston’s Road in Blackwall near the entrance to Millwall Docks.
It is part of the vast New District development to create a new mixed-use scheme across 22 acres.
The London Fire Brigade said: “Various building materials were damaged by the fire.”