Four fire engines and around 25 firefighters were called to a house fire on Mays Lane in Barnet.
Firefighters tackled a fire in a semi-detached house, where a large part of the ground floor was damaged by the fire. There were no injuries reported.
The Brigade's Fire Investigators believe the fire was accidental and caused by a toaster.
A London Fire Brigade spokesperson said: "Avoid keeping items such as toasters under cupboards or in contact with combustible items such as tea towels or kitchen roll to prevent heat build-up.
"It's also important to make sure you keep toasters clean to help prevent fires."
The Brigade was called at 1230 and the fire was under control by 1342. Fire crews from Barnet, Finchley, Enfield and Hornsey fire stations attended the scene.