Four fire engines and 21 firefighters and officers were called to an advertising hoarding alight in The Grove, Stratford.
One advertising hoarding was destroyed by fire. Part of the external fascia of two flats was also damaged by fire.
Two adults and two children were lead to safety from a basement flat and were treated at the scene for smoke inhalation before being taken to hospital by London Ambulance Service crews.
The Brigade was called at 1848 and the fire was under control at 1952. Fire crews from Plaistow, Leyton, Poplar and Homerton fire stations attended the scene.