Four fire engines and around 25 firefighters tackled an office fire on Lincoln's Inn Fields in Holborn.
Half of a storage room on the fourth floor of the five-storey office building was damaged by fire. There are currently no reports of any injuries.
The Brigade was called at 0615 and the fire was under control by 0750. Crews from Soho, Euston and Dowgate fire stations attended the scene.
The cause of the fire is under investigation.