Twelve fire engines and around 80 firefighters were called to a flat fire on Dalston Lane in Hackney.
Firefighters tackled a fire at a four-storey block of flats. A flat on the second floor and a flat on the third floor were damaged by the fire. There were no reports of any injuries.
Station Commander Chris Swallow said: "Firefighters arrived to find smoke coming from the top floor of the flat.
"Dalston Lane was closed whilst we worked to make the scene safe. This was causing congestion so we asked people to avoid the area where possible."
The Brigade was called at 0920 and the fire was under control by 1244. Firefighters from Homerton, Stoke Newington, Leyton, Islington and other surrounding fire stations attended the scene.
The fire is believed to have been caused by resistive heating involving the flex outlet (which allows a fixed appliance to be connected to the building wiring) for an electric combi-boiler.