Four fire engines and around 25 firefighters were called to a fire at a fast food takeaway shop with flats above on Streatham High Road in Streatham.
Part of the ground floor of a mid-terraced takeaway shop and part of the extraction system was damaged by fire. Ten people left the flats above the shop before the Brigade arrived. There were no reports of any injuries.
A London Fire Brigade spokesperson said: "We'd like to remind restaurant and takeaway owners to ensure they don't have dirty ducting. If you don't clean the ducting in your extraction system regularly, you're at a greater risk of ducting fires.
"You should also make sure you keep the hob, cooker hood and extractor fan clean too – built up fat and grease can ignite and cause a fire."
The Brigade was called at 0424 and the fire was under control by 0535. Fire crews from Norbury, West Norwood and Tooting fire stations attended the scene.
The cause of the fire is believed to have been accidental.