Four fire engines and around 25 firefighters were called to a house fire on Green Lane in Morden.
The ground floor of a mid-terraced house was destroyed by fire and part of the loft area was also damaged by the blaze. One child was treated on scene by London Ambulance Service crews and two women were taken to hospital.
The Brigade was called at 0212 and the fire was under control by 0446. Fire crews from Sutton, Mitcham, Wimbledon and Wallington fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.