Five fire engines and around 30 firefighters were called to a fire at a block of flats on Bell Farm Avenue in Dagenham.
A fire occurred in an electrical intake cupboard on the second floor of the building. Part of a second-floor flat also sustained damage as a result of the fire. Three adults and five children were taken to hospital by London Ambulance Service as a precaution.
Due to a loss of power to the building, all residents have been temporarily displaced from the building. A rest centre has been set up and being led by Barking & Dagenham Council.
London Fire Brigade Assistant Commissioner Pat Goulbourne said: "We have local officers on-site at the rest centre supporting residents alongside our partners. We will continue to liaise with the community and provide support tonight and over the coming days."
The Brigade was called at 1820 and Control Officers mobilised crews from Dagenham, Ilford, Romford and surrounding fire stations to the scene. The fire was extinguished by London Fire Brigade crews wearing breathing apparatus by 1957.
The cause of the fire is under investigation.