Twelve fire engines and around 80 firefighters tackled a fire at a suspected cannabis factory at a house on Knebworth Avenue in Walthamstow.
The first floor, staircase and roof were destroyed and half of the ground floor was damaged by the fire. There were no reports of any injuries.
The fire was accidental and is believed to have been caused by tampering with the property's electrical supply.
A London Fire Brigade spokesperson said: “Cannabis factory fires can be particularly dangerous because of the way criminals use unsafe wiring to illegally obtain electricity in order to grow the plants.
"They're often in top floors or lofts which means when a fire takes hold it spreads, destroying roofs and damaging neighbouring buildings.
"Firefighters can also be exposed to risks when dealing with the fires because of bad wiring and traps at some of the properties.
"It's important that people know the key signs and inform the police so that they can act swiftly to prevent these dangerous fires from happening."
The Brigade's 999 Control officers received the first of two calls alerting them to the fire at 0252. They deployed crews from Walthamstow, Chingford, Woodford, Leyton, Tottenham, Edmonton, Homerton, Stratford, Enfield and Holloway fire stations. The fire was under control by 0451.