Four fire engines and around 25 firefighters tackled a fire at a building under construction on Fitzroy Street in Fitzrovia.
An industrial boiler on the sixth floor of the building was destroyed by fire. Around 130 people left the building before the Brigade arrived and two men were treated on scene by London Ambulance Service crews.
The Brigade was called at 1417 and the fire was under control by 1536. Fire crews from Paddington, Islington, Homerton and Shoreditch fire stations attended the scene.
The cause of the fire is under investigation.