Four fire engines and around 25 firefighters were called to a flat fire at a block of flats on Rosalind Close in Mill Hill.
A small part of a flat on the second floor of a four-storey block was damaged by the fire. Around 30 people left the building before the Brigade arrived. Two people were treated at the scene and one was taken to hospital by London Ambulance Service crews.
The Brigade's Fire Investigators believe the fire was caused by items left close to the hob.
A London Fire Brigade spokesperson said: "You should never place anything that can catch fire near to the hob.
“Keep all objects, like tea towels, cloths and plastic bowls, well away from the hob and always check it’s turned off when you've finished cooking."
The Brigade was called at 2210 and the fire was under control by 2258. Fire crews from Mill Hill, Finchley and Hendon fire stations were at the scene.