The blaze occurred in an electrical intake cupboard on the second floor of a building in Bell Farm Avenue.
The London Fire Brigade (LFB) was called at 6.20pm yesterday (October 11) and crews were mobilised from Dagenham, Ilford, Romford and surrounding fire stations.
Five fire engines and around 30 firefighters attended the scene.
LFB confirmed that three adults and five children were taken to hospital by the London Ambulance Service as a precaution.
All residents have been temporarily “displaced” from the building due to a loss of power.
A “rest centre” has been set up and being led by Barking and Dagenham Council.
The fire was extinguished by LFB crews wearing breathing apparatus by 7.57pm and the cause of the blaze is under investigation.
Part of a second-floor flat also sustained damage as a result of the fire.
LFB 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.”
Barking and Dagenham Council has been contacted for further information on the rest centre.
