British authorities expect to spend weeks, even months, identifying the victims of the massive fire that engulfed a London high-rise this week, warning on Thursday that they may not be able to identify everyone.
At least 17 people were killed in the disaster, although that figure is expected to rise.
"There is a risk we may not be able to identify everybody," Commander Stuart Cundy said at a press briefing on Thursday.
"The process will be very long. We're talking weeks, we're talking months," he added.
Of the 17 victims that have so far been confirmed, six have been identified.
Their bodies were recovered outside the building and police said it was for now "impossible to say how they died".
The bodies of the remaining 11 victims are still inside the smouldering tower.
"They are simply not recognisable because of the fire," Fiona McCormack, one of the Metropolitan Police's senior identification managers, said.
Police use one of three ways to identify the victims, McCormack explained: dental records, fingerprints and DNA.
Using dental records "is the best one for very quick identification," as fingerprints and DNA are "much more difficult to get".
If those methods fail, police look for secondary identification methods such as tattoos, scars or medical devices like pacemakers.
But for now, authorities are still struggling to find out how many people were actually in the 24-storey building when the fire started in the early hours of Wednesday.
Six hundred people are believed to be residents of the Grenfell Tower.
A "good half" of the building has yet to be searched according to Fire Commissioner Dany Cotton, who explained that additional shoring up was needed for firefighters to access the upper floors.
But Cundy sought to downplay the number of missing people on Thursday saying that while 400 people had been reported missing, "it is an assumption".
"A lot of people managed to get outside themselves and 65 were rescued," he said.
"From a personal perspective, I like to hope it is not going to be triple figures".
At least 17 dead in London tower block fire
At least 17 people are confirmed dead in the massive fire that engulfed a London tower block on Wednesday, police said.
"Sadly I can confirm that the number of people that have died is now 17," Metropolitan Police commander Stuart Cundy said in a televised statement on Thursday.
12 dead as fire engulfs London tower block
At least 12 people perished on Wednesday after a massive inferno tore through a London apartment block, with witnesses reporting terrified residents had leapt from the tower and dropped their children in a desperate bid for survival.
As smoke continued to billow from the gutted building, survivors voiced anger over longstanding safety fears at the 24-storey Grenfell Tower, which was home to between 600 and 800 people.
Parents wrapped wet towels around their children as they tried to escape, while others were seen desperately waving for help from the higher floors, which firefighters could not reach at the blaze took hold.
"There are now 12 people that have died that we know of," police commander Stuart Cundy told reporters at the scene.
"I do anticipate that the number of fatalities will sadly increase" he said, adding that he did not expect fire crews hunting through the debris to find any survivors.
Seventy-eight people were being treated in hospitals, 18 of whom are in a critical condition.
The alarm was raised just before 1:00 am (0000 GMT) and within an hour flames had engulfed the entire block of 120 flats.
More than 200 firefighters had been tackling the blaze and managed to rescue 65 people.
Some 16 hours on, pockets of flame were still burning inside, and fire crews had reached the top. They had used drones to examine the upper floors.
Blazing chunks of debris fell from the wrecked building, a 1970s local authority-built block in the working-class area of north Kensington, just streets away from the wealthy homes of Notting Hill.
Residents claimed the fire spread on the exterior of the tower, which had been covered in cladding in a major refurbishment completed last year.
The London Fire Brigade said the cause of the fire was under investigation, but its chief Dany Cotton said she had "never seen anything on this scale" in her 29-year career.
Six dead in London tower block fire, toll expected to rise
Six people were confirmed dead in a massive fire that engulfed a London tower block before dawn on Wednesday and the number is expected to rise, police said.
"I can confirm six fatalities at this time but this figure is likely to rise during what will be a complex recovery operation over a number of days," police commander Stuart Cundy said in a statement.
'A lot of people' unaccounted for after tower blaze
"A lot of people" are still unaccounted for after a massive blaze in a London tower block, and fire crews only managed to reach the 12th floor at the height of the fire, mayor Sadiq Khan said on Wednesday.
"A lot of people are unaccounted for. Some of them could have found safe refuges in the homes of their neighbours or their friends," Khan told Sky News television as smoke billowed from the charred 27-storey building.
'A number of fatalities' in London tower block fire
"A number" of people have been killed in a massive fire in a west London apartment block on Wednesday, London Fire Brigade chief Dany Cotton told reporters at the scene.
"There have been a number of fatalities. I cannot confirm the number at this time due to the size and complexity of the building," Cotton said.
At least 30 injured in London tower blaze
At least 30 people were injured in a fire that swept through a 27-storey London tower block early Wednesday, the emergency services said.
"We can confirm that we have taken 30 patients to five London hospitals following the incident," Stuart Crichton, assistant director of operations at the London Ambulance Service said, adding that more than 20 ambulance crews as well as a "hazardous area response team" were at the scene.
Fire engulfs tower block in west London
A massive fire ripped through a 27-storey apartment block in west London in the early hours of Wednesday, trapping residents inside as 200 firefighters battled the blaze.
Witnesses said they heard screaming from the upper floors as the flames rose in the night and one desperate resident could be seen waving a white cloth from a top floor window.
Police said "a number of people are being treated for a range of injuries", including at least two for smoke inhalation.
Four hours after the alarm was raised, flames could still be seen on several floors of the blackened residential building, which was shrouded in a cloud of thick black smoke.
Large pieces of debris could be seen falling from Grenfell Tower, a 1970s block in the working-class north Kensington area - a short distance from chic Notting Hill.
Frantic families at the scene attempted to call their loved ones, fearing they could be stuck inside, and were being directed by police to a nearby restaurant where some of the injured were being treated.
The fire brigade said 40 fire engines and 200 firefighters had been called to the blaze in Grenfell Tower, which has 120 flats.
The ambulance service said it had sent more than 20 ambulance crews to the scene.
"Fire is from 2nd to top floor of 27 storey building," the fire service said on Twitter.
Firefighters at the scene said they had managed to evacuate residents up to the 11th floor.
Police were also clearing out nearby buildings because of fears about falling debris and shut down a section of the A40 highway - a normally busy thoroughfare into London.
A London Underground line passing the area near Latimer Road station was also shut down.
"Firefighters wearing breathing apparatus are working extremely hard in very difficult conditions to tackle this fire," London Fire Brigade assistant commissioner Dan Daly said.
"This is a large and very serious incident and we have deployed numerous resources and specialist appliances," he said.
London mayor Sadiq Khan also declared it a "major incident".
Actor and writer Tim Downie, who lives nearby, said: "It's horrendous. The whole building is engulfed in flames. It's gone. It's just a matter of time before this building collapses".
Police said in a statement they were called at 1:16am (0016 GMT) "to reports of a large fire at a block of flats in the Lancaster West Estate".
The apartment block was built in 1974.
Local residents had warned a year ago about a potential fire risk caused by rubbish being allowed to accumulate during improvement works.
"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," it said.