Four fire engines and around 25 firefighters were called to a house fire in Staines Road, Ilford.
Half of the ground floor of the mid-terraced house and part of the first floor were damaged by fire. Three men and one woman left the property before crews arrived.
The Brigade was called at 0014 and the fire was under control by 0100.
Fire crews from Ilford, Stratford and Dagenham Fire Station were at the scene.
The cause of the fire is believed to be an electrical fault.