Four fire engines and around 25 firefighters tackled a shed fire on Hillier Gardens in Croydon.
Two garden sheds were destroyed by the fire. There were no reports of any injuries.
Two cylinders were cooled to an ambient temperature and removed as a precaution, as some cylinders can explode when exposed to heat.
The fire is believed to have been accidental and was caused by an unattended bonfire.
A London Fire Brigade spokesperson said: "We would urge people to consider if their bonfire is necessary and to take care if you’re burning waste at home or at work.
"If you’re having a bonfire never leave it unattended and consider your neighbours when you do decide to have a fire in your garden.
"Make sure you build it well clear of buildings, garden sheds, fences and hedges and never use flammable liquids to start it or burn dangerous items such as aerosol cans. Always keep a bucket of water or a hosepipe nearby in case of fire.
“Always check your local authority’s advice on bonfires and follow our safety tips."
Control Officers took the first of 12 calls at 0247 and mobilised crews from Croydon, Wallington, Purley and Addington fire stations to the scene. The fire was extinguished by 0420.