The Brigade’s fire investigators believed the fire was caused after a chair was placed too close to a halogen heater and caught alight.
Around half of the ground floor of the property was damage by fire.
The alarm was raised after the occupants of the property heard a smoke alarm sounding. Two men were treated at the scene for smoke inhalation before being taken to hospital by London Ambulance Service crews. A woman was also assessed at the scene. Firefighters rescued five dogs from the first floor of the property.
A London Fire Brigade spokesperson said: “If you use an electric heater this winter, never leave it unattended. It’s really important to ensure they are placed well away from clothes, duvets and other items that can catch fire if they get too close.“
The Brigade was called at 1817 and the fire was under control at 2009. Four fire engines and around 25 firefighters from New Cross, Greenwich, Deptford and Lewisham fire stations attended the scene.