The blaze, believed to have been started by a charging electric scooter, broke out near the Shepherds Bush area of London.
Eight fire engines were deployed to the scene as half a flat was alight.
A London Fire Brigade statement reads: "Eight fire engines and around 60 firefighters and dealing with a fire in a high rise block on Queensdale Crescent in Shepherds Bush.
"Half of a flat on the 12th floor is alight. More soon."
The scene of the fire in London
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The flat where the blaze started
KEVIN COOMBS
The incident was reported at 9.23am on Tuesday and the cause remains unknown.
The building is less than a mile away from Grenfell Tower where 72 people died following a blaze in 2017.
Multiple ambulances were dispatched to the scene.
Hammersmith and Fulham Borough Labour councillor Stephen Cowan said a male individual was understood to have poured water on an e-scooter when it caught fire causing “billowing smoke”.
Mr Cowan said: “What I’ve been advised is that there was a fire started early in the morning by an electric scooter.
"They were charging an electric scooter in the flat, it caught fire, the individual had the presence of mind to pull the plug on it, and then he threw water on it.
“That caused billowing smoke. Smoke went everywhere. Automatically the fire alarms kicked in.”
Firefighters at the scene
KEVIN COOMBS
London Ambulance Service confirmed they were "responding to a fire in Queensdale Crescent, W11, alongside colleagues from the London Fire Brigade".
A statement added: "We have dispatched multiple resources to the scene and are treating a number of patients. More updates to follow."
Conservative MP for Kensington Felicity Buchan described news of the fire as “very concerning” and said aerial appliances had been deployed to the scene.
Liiban Shakat, of Stebbing House, Shepherd’s Bush, west London, said a visitor woke him up on Tuesday morning with a “black mouth” from the smoke and led him to the guest bedroom, which was engulfed in flames.
The 38-year-old, who has lived in the building for more than 20 years, recalled watching the Grenfell Tower blaze from the same flat that caught fire on Tuesday.
Speaking to reporters outside the building, he said: “He forces me to wake up. I follow him. I went into the room and the whole room is on fire. I ran to the sink, I got a bucket of water and I tried to discourage the fire and then it got worse.”
A later statement for the London Fire Brigade read: "We were called at 9.45am to reports of a fire at a block of flats on Queensdale Crescent.
"We sent resources to the scene, including two ambulances and our Hazardous Area Response Team.
"Two patients were assessed at the scene and another was treated and taken to hospital."