London Fire Brigade said the fire had engulfed all floors from the second to the top of the Grenfell Tower.
Fire engulfed a 27-storey block of flats in central London on Wednesday, killing some people, injuring at least 50 more and trapping some residents asleep inside the towering inferno.
The fire engulfed at Grenfell Tower on Latimer Road in Lancaster West Estate in West London.
London Fire Brigade chief Dany Cotton told reporters at the scene that there have been a number of fatalities. "In my 29 years of being a fire fighter, I have never ever seen anything of this scale. I am very sad to confirm that there have been a number of fatalities, I cannot confirm the number at this time due to the size and complexity of this building."
“The cause of the fire is not known at this stage, and clearly we will be here all day and will be in a providing further updates, working with the police and ambulance service,” London Fire Brigade said in a Facebook Post.
“Further information for the public will be made available shortly, including advice for those concerned about those they are worried about and the emergency services will be working with all agencies, including the local authority to support all of those affected by this incident,” it added.
London Ambulance Service said more than 50 people had been taken to hospital.
"Officers, the London Fire Brigade and the London Ambulance Service are currently at the scene. An evacuation process is underway," said the Metropolitan Police.
More than 20 ambulance crews were at the scene.
London Mayor Sadiq Khan said a 'major incident' had been declared. Police closed the A40, a major road leading out of west London, while some parts London's underground train network were closed as a precaution.
The cause of the fire, which broke out just before 1:00 am (GMT), is not known, the Fire Brigade said.
Some people were trapped in the fire, with residents desperately shouting for help from windows on upper floors as the fire spread, some British media reported.
"It has burned through to its very core. It looks very bad, very very bad. I've never seen anything like this. It's just such a big fire. The whole building is just crumbling. It's just billowing black smoke," an eyewitness told the BBC.
Residents said repairs, including the addition of some sort of cladding, had been made to the exterior of the block recently.
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