Six fire engines and around 40 firefighters were called to a fire at a restaurant with flats above on Brixton Hill, Brixton.
Around half of the restaurant's mezzanine was damaged by fire.
Station Manager John Lewis, who was at the scene, said: "The fire was contained to the front of the restaurant but firefighters evacuated one resident from a flat above as a precaution.
"Crews cooled one 15kg LPG gas cylinder to ambient temperature and removed it from the scene."
The Brigade was called at 0938 and the fire was under control at 1202. Fire crews from Brixton, West Norwood, Lambeth, and Tooting fire stations attended the scene.
The cause of the fire is believed to be due to the build-up of grease in the extractor hood in the kitchen.