Six fire engines and around 40 firefighters were called to a fire at an office block under construction on Wimpole Street in Marylebone.
Firefighters tackled a blaze in a void between the ground and first floors of the six-storey building. Around 75 people left the building before the arrival of the Brigade. There were no reports of any injuries.
The Brigade was called at 0927 and the fire was under control by 1114. Fire crews from Soho, Paddington, Euston and Hornsey fire stations were at the scene.
The fire is believed to be accidental and caused by hot works.