Five fire engines and around 35 firefighters were called to a fire in a residential garden on Fitzalan Street in Lambeth.
Three garden sheds at the rear of two houses converted into flats were destroyed. A small part of a ground-floor flat was also damaged by fire. Firefighters wearing breathing apparatus rescued a woman from the building. She was taken to hospital by London Ambulance Service crews alongside another man.
Two gas cylinders were involved in the fire and were removed and cooled to an ambient temperature as a precaution as some cylinders can explode when exposed to heat.
The fire is believed to have been accidental and caused by a bonfire spreading out of control.
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 if you do decide to have a fire in your garden.
"Make sure you build it 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 check your local authority’s advice on bonfires and follow our safety tips on our website.”
The Brigade’s Control Officers took the first of nearly 30 calls to the fire at 1926 and gave vital fire survival guidance to those at the incident on how to stay safe before firefighters arrived. Crews from Dowgate, Soho, Old Kent Road, Lambeth and surrounding fire stations attended the scene. The fire was under control by 2123.