A Wimbledon maisonette blaze is believed to be caused by a faulty extension cable.
The fire damaged two double mattresses and an electrical socket in the upper floor bedroom of the property in Windlesham Grove.
Fire Investigators believe the fire started when a portable heater/cooler plugged into an extension cable was left on in the bedroom. They think a faulty extension lead caught fire while the residents were out.
A woman and her three children returned to the maisonette to find the smoke alarms activated and smoke coming out of a window.
Firefighters worked hard to contain the blaze and ensure it did not spread to any of the adjoining properties.
Four fire engines and 21 firefighters from Wandsworth, Wimbledon, Fulham and Battersea fire stations attended the scene.
The Brigade was called at 1658 and the fire was under control by 1748.