Here is what we know so far.
How many victims in the London Fire?
Police say at least 17 people were killed in the fire that broke out in the early hours of Wednesday at the 24-storey Grenfell Tower in west London, and they expect the number to rise as emergency workers make their way through the charred wreck of the building.
Fire Commissioner Dany Cotton said firefighters had been able to search only half of the building "in detail" because of structural safety concerns, and that sniffer dogs were being used to find bodies.
Cotton had earlier told Sky News it would take weeks to clear the building, and that "tragically now we are not expecting to find anyone else alive."
The tower was home to about 600 residents and had only one stairway through which people could escape.
Seventy-four people were being treated in hospitals, 20 of them in critical condition.
London Fire: What happened?
Fire services said they received the first call at 00:54 am on Wednesday and were on scene at the public housing complex within six minutes.
The concrete block was built in 1974 in the working-class area of north Kensington, close to the wealthy Notting Hill district which contains some of the most expensive homes in the world.
Witnesses reported the entire building was on fire by around 2:00 am (0100 GMT).
Survivors said they saw the flames racing up the exterior of the building, which had recently been covered in cladding during a major refurbishment finished last year.
The 8.7 million pounds (9.9 million euro, $11 million) refurbishment also included new windows and heating systems.
Questions are growing about how the flames spread so quickly, engulfing its 120 apartments.
"It appears that the external cladding has significantly contributed to the spread of fire," said Angus Law from the BRE Centre for Fire Safety Engineering at the University of Edinburgh.
London Fire: What were Grenfell Tower residents' concerns?
According to the BBC, the cladding had a plastic core, and was similar to that used by high-rise buildings in France, the United Arab Emirates and Australia which had also suffered fires that spread.
There were questions about why there was no sprinkler system in Grenfell Tower which could have helped stop the fire spreading, or any central smoke alarm system that would have woken sleeping residents.
Construction firm Rydon, which completed the refurbishment in 2016, said the work "met all required building control, fire regulation and health and safety standards".
But David Collins, former chairman of the Grenfell Tower Residents' Association, said the building's management had failed to listen to residents' calls for improvements on fire safety.
"If the same concerns were had in a wealthy part of Kensington and Chelsea they would have got resolved, but here they didn't get resolved," Collins told AFP.
"This is a multi-ethnic, multicultural, diverse community that just didn't get served by the people representing them."
Local residents had warned a year ago about a potential fire risk caused by rubbish being allowed to accumulate during the refurbishment.
"This matter is of particular concern as there is only one entry and exit to Grenfell Tower during the improvement works," read a blog post by the Grenfell Action Group.
"The potential for a fire to break out in the communal area on the walkway does not bear thinking about as residents would be trapped in the building with no way out."
Some residents said the official advice was that people should stay inside in the event of a fire.
Public mobilises in London Fire
The disaster triggered a wave of mourning in a country already battered by a string of terror attacks.
More than 480,000 pounds had been raised online for the victims by Thursday morning, while local community centres were inundated by donations of clothes and food.
Volunteers in Glasgow -- 550 kilometres (350 miles) away -- sent a truck laden with nappies and other supplies.