Ten fire engines and around 70 firefighters tackled a fire at a warehouse on Lombard Road in South Wimbledon.
Part of the ground floor and exterior of the warehouse was damaged by the fire. A stack of timber was destroyed by fire. Two people suffering from smoke inhalation were treated at the scene by London Ambulance Service crews .
Station Commander Tom Conlon, who was at the scene, said: "The fire was producing heavy smoke in the local area. People were advised to keep their windows and doors closed and to avoid the area."
The Brigade's drone team assisted by providing an aerial view of the incident. Two 32-metre turntable ladders were used to help extinguish the fire.
The fire is being treated as accidental and is believed to have been caused by the unsafe disposal of smoking materials.
A London Fire Brigade spokesperson said: "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's 999 Control Officers received 12 calls about the fire.
The Brigade was called at 1455 and the fire was under control by 1932. Crews from Wimbledon, Mitcham, New Malden, Sutton, Kingston, West Norwood and surrounding fire stations attended the scene.