Four fire engines and around 25 firefighters attended a fire at an industrial unit on Ellis Road in Mitcham.
A ground floor office was destroyed by fire. There were no reports of any injuries.
The Brigade received the first of three calls at 2242 and Control Officers mobilised crews from Mitcham, Wallington and Norbury fire stations to the scene. The fire was extinguished by 2345.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police.