Four fire engines and around 25 firefighters were called to a fire at an office block on Regents Park Road in Finchley.
Half of the first floor of the three-storey building was damaged by the fire. There were no reports of any injuries.
The Brigade was called at 0903 and the fire was under control by 1023. Fire crews from Finchley and Hendon fire stations attended the scene.
The cause of the fire is believed to be electric due to a failure of a laptop battery pack.