Six fire engines and around 40 firefighters attended a fire at a mixed-use building on Aylesbury Street in Clerkenwell.
A split-level maisonette on the upper floors of the six-storey building was partially damaged by fire, along with its balcony area. There were no reports of any injuries.
One gas cylinder was removed from the scene and cooled it to an ambient temperature as a precaution, as some cylinders can explode when exposed to heat.
The fire is believed to have been caused by the unsafe disposal of smoking materials.
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.
“Firefighters recommend that you have a look at our online Home Fire Safety Checker to make sure there are no hidden hazards in your home.
“The online tool will ask you a series of questions that will help us work out the level of risk in your home, or the home of someone you care for. It only takes a few minutes to get tailored advice to keep yourself and loved ones safe from fire.”
The Brigade received the first of six calls about the fire at 1650 and Control Officers mobilised crews from Islington, Soho, Dowgate, Lambeth and Bethnal Green fire stations to the scene.
A 32-metre turntable ladder from Soho Fire Station and was used as a water tower to help extinguish the fire from height. One of the Brigade's drones was also deployed to provide the Incident Commander with a greater situational awareness of the incident.
The fire was extinguished by 1951.