Two fire engines and around 10 firefighters were called to a fire at a car workshop on Finch Street, Depford.
A section of the workshop was damaged by fire. Firefighters removed five gas cylinders from the premises and cooled them to ambient temperature as some cylinders can explode when exposed to heat.
The cause of the fire is believed to have been due to a discarded cigarette.
A London Fire Brigade spokesperson said: “If you're 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 that will cause a lot of damage, but also and may cost lives.”
The Brigade was called at 1919 and the fire was under control at 2225. Fire crews from Depford and Greenwich attended the scene.