The unsafe disposal of smoking materials is believed to have caused a blaze at a house in Carmen Street, Poplar.
Fifty percent of the first floor was damaged by fire. Six people left the building before the Brigade arrived and there were no reports of any injuries.
A London Fire Brigade spokesperson said: “If you're a smoker it’s absolutely vital you ensure your cigarette is completely out when you’ve finished smoking it.
“If you don’t, you risk causing a fire which could not only destroy your home, but also cost you your life.”
The Brigade was called at 1739 and the fire was under control by 1823. Fire crews from Poplar, Millwall, Shadwell and Plaistow fire stations attended the incident.