Four fire engines and around 25 firefighters were called to a warehouse fire on Lansdowne Hill in West Norwood.
Part of the ground floor and the roof of a single-storey, derelict warehouse with a mezzanine floor were damaged by fire. There were no reports of any injuries.
The Brigade’s Fire Investigators believe the fire was accidental and caused by smoking materials.
A London Fire Brigade spokesperson said: “On arrival, crews discovered a small fire in a room used to discard domestic rubbish which had spread into the roof area.
"We'd rather you didn't smoke at all, but if you are a smoker it's absolutely vital you ensure your cigarette is completely out when you've finished smoking it.
"If you don't, you risk causing a fire which could not only destroy properties but also cost you your life."
The Brigade was called at 2115 and the fire was under control by 2302. Fire crews from West Norwood, Norbury, Brixton and Clapham fire stations attended the scene.