According to several witnesses, the blaze started on one side of the tower block, before sweeping around the building and engulfing it in flames from the second to the top floor.
What caused it?
The cause of the fire is so far unknown, but residents had previously raised concerns that a 'catastrophic' event could happen. An action group of Grenfell residents said their warnings fell on "deaf ears" after highlighting safety concerns about the block.
The group said there was one entry and exit to Grenfell Tower during improvement works at the block in Latimer Road and it had issues with evacuation procedures at the building.
Following the fire, the group posted: "All our warnings fell on deaf ears and we predicted that a catastrophe like this was inevitable and just a matter of time."
There are five theories being widely speculated on.
1. Gas explosion - Residents said refurbishment work had recently been carried out with work on the gas supply to the flats.
2. Faulty fridge - Witnesses described hearing one distressed resident apparently telling neighbours his faulty fridge caused the blaze.
3. Faulty wiring - One of the safety issues they highlighted was faulty wiring and said a disaster cause by the problem was narrowly averted four years ago.
4. Cladding on outskirts - Grenfell Tower was fitted with zinc rainscreen cladding and glazed curtain walling after a £10 million refurbishment. Experts have claimed this could have exacerbated the spread of the fire.
5. Lack of sprinklers/exits - Labour MP Jim Fitzpatrick said the Government has resisted calls to install sprinkler systems in high-rise blocks in the wake of the Lakanal House tragedy. The local Action Group also warned that there were not enough entries and exits to cope with a catastrophic event
How many people have been killed and injured?
So far there have been twelve confirmed deaths, but the Fire Service have suggested that number is likely to rise further, and it is unlikely any more survivors will be recovered from the building.
The ambulance service has now said 68 patients have been taken to six hospitals across London, with 18 people in critical care.
A further 10 patients made their own way to hospital.
A 'significant number' of people are still unaccounted for.
Police have said a number of people are being treated for a range of injuries.
The leader of Kensington and Chelsea Borough Nick Paget-Brown said "several hundred" people would have been in the block when the fire broke out
The Metropolitan Police have set up a casualty bureau for anyone concerned about their friends and family.
What about the missing?
A number of children and elderly people are missing, as friends and family have appealed via social media for information on their whereabouts.
Among them are a 12-year-old Jessica Ospina.
Jessica's other aunt, Sandra, wrote: "If anyone sees Jessica she should come to The Harrow Centre where the family are waiting for her. Or speak to any police officer to guide her".
Hamid Ali Jafari said that he his 82 year-old father Ali Yawar Jafari had not been seem since the early hours of the morning as the family were trying to escape the blaze.
He said: "He was with my mother and sister in the lift and she said the lift stopped on the tenth floor and he said there was too much smoke and he couldn't breathe and he got out of the lift and then the doors shut and it didn't stop again till the ground floor."
What did witnesses see?
Witnesses have spoken of hearing screams and seeing some people escaping using bedsheets as improvised rope ladders.
London Fire Brigade told people to put wet cloths over their mouths to avoid inhaling smoke as they made their escape.
The building has been gutted and the families left only with the bedclothes they were wearing when they were evacuated.
There were reports of a strong smell of burning plastic, thought to be white cladding that was installed on the building last year as part of a £10million refurbishment.
Who is on the scene?
Fire crews have been sent from North Kensington, Kensington, Hammersmith and Paddington and surrounding stations.
In all 40 fire engines and around 200 firefighters have been deployed along with police. The London ambulance service has sent its Hazardous Area Response Team.
What do we know about the building?
Grenfell Tower was completed in 1974, so would have needed to comply with strict new regulations which ensured buildings would not fall down in the event of a blast, or a major fire. However recent cladding works to the outside may have exacerbated the fire, according to experts at the University of Edinburgh.
Have there been other tower block fires in London?
In July 2009, six people were killed at more than 20 injured when in a blaze at Lakanal House, a tower block in Camberwell, south east London.
In May 1968 four people were killed and 17 injured when Ronan Point, a tower block in Newham, east London, partially collapsed after a gas explosion, which blew out several load-bearing walls.
