Four fire engines and around 25 firefighters were called to a derelict health centre on Moorfield Road in Enfield.
Firefighters tackled a small fire on the first floor of a derelict building, which caused a small amount of damage. The Brigade's Control Room has received 21 calls about the fire.
The Brigade was called at 1244 and the fire was under control by 1349. Fire crews from Enfield, Edmonton and Chingford fire stations attended the scene.
The cause of the fire will be investigated.