Eight fire engines and around 60 firefighters were called to a fire at a scrapyard on Burnham Way in Lower Sydenham.
Around seven tonnes of scrap metal, including vehicles, were alight at the scrapyard. Around eight people left the site before the Brigade arrived and one man was treated on scene by London Ambulance Service crews.
Station Commander Keith Sanders, who was at the scene, said: "The fire was extremely visible and our 999 Control Officers received 30 calls alerting them to the fire.
"Due to the amount of smoke, local residents were advised to keep their windows and doors closed."
The Brigade was called at 1501 and the fire was under control at 1701. Fire crews from Forest Hill, Beckenham, Lewisham, Bromley, Lee Green and surrounding fire stations attended the scene.
The fire is believed to have been accidental, with the most likely cause being electrical arcing from a battery-powered tool igniting petrol vapour from a nearby open petrol can.