Six fire engines and around 40 firefighters were called to fire at a nightclub and office block on Old Street in Shoreditch.
A plant room in the basement of the building was destroyed by fire. There were no reports of any injuries.
Station Commander Brett Loft, who was at the scene, said: “On arrival there was heavy smoke logging in a mail room on the ground floor and in several offices in the building. Upon further investigation crews found a fire in a plant room in the basement.
“There were road closures in place whilst crews worked quickly to make the scene safe.”
The Brigade was called at 1710 and the fire was under control by 1833. Fire crews from Shoreditch, Whitechapel, Bethnal Green, Islington and Shadwell fire stations attended the scene.
The cause of the fire is under investigation.