Four fire engines and around 25 firefighters were called to a fire at a multi-storey car park on Wandle Road in Croydon.
A disused electrical transformer was destroyed by the fire on the ground floor.
The Brigade's 999 Control Officers took 17 calls to the blaze.
The Brigade was called at 2355 and the fire was under control by 0106. Fire crews from Croydon, Norbury and Woodside fire stations were at the scene.