Six fire engines and around 40 firefighters were called to a shipping container alight in a commercial yard on Oaks Road in Croydon.
Two portable cabins, two shipping containers and a lorry were destroyed by fire. Part of three further shipping containers were also damaged by the blaze. There were no reports of any injuries.
A cylinder was cooled to an ambient temperature and removed as a precaution, as some cylinders can explode when exposed to heat.
The fire was discovered when a nearby resident heard a loud bang. They went into their garden to investigate and saw most of the structures in the yard alight and called 999.
The Brigade was called at 1948 and the fire was under control by 2135. Fire crews from Addington, Woodside, Purley, Croydon, Sidcup and Orpington fire stations attended the scene.
The cause of the fire is under investigation.