At least 17 people died in a massive fire that engulfed a west London block of flats, police said, as they warned that figure could rise further.
Earlier, the fire service said rescuers did not expect to find any more survivors in the smouldering ruins of Grenfell Tower, in north Kensington.
Specialist dogs are to be sent in to search for evidence and identification of people still inside.
The Queen has said her "thoughts and prayers" are with families.
People have been desperately seeking news of missing family and friends.
More than 30 people remain in hospital - 17 of whom are in a critical condition.
Prime Minister Theresa May, who made a brief private visit to the scene, has promised a full investigation, as questions are asked about the speed at which the fire spread.
Firefighters were called to the 24-storey residential tower in the early hours of Wednesday, at a time when hundreds of people were inside, most of them sleeping.
Many were woken by neighbours, or shouts from below, and fled the building. Fire crews rescued 65 adults and children, but some stayed in their homes, trapped by smoke and flames.
On Thursday morning, London Fire Commissioner Dany Cotton said her crews had identified a "number of people, but we know there will be more".
The size of the building means it could take weeks, she added.
Asked how many were still missing, Met Police Commander Stuart Cundy said it would be "wrong and incredibly distressing" to give a number.
"I know one person was reported 46 times to the casualty bureau," he said.
A brief search of all floors in the tower had been carried out, but the severity of the fire and amount of debris meant a thorough search would be "difficult and painstaking", Commander Cotton said.
Temporary structures will be built inside the block in order to shore it up before more thorough work can begin.
The cause of the fire, which took more than 24 hours to bring under control, remains unknown.
Throughout the morning, only smoke was seen coming from the charred building, but by Thursday lunchtime flames flared up again on one of the lower floors.
Dozens of people left homeless spent the night in makeshift rescue centres, as well-wishers signed a wall of condolence near the site.
London-born singer Adele and her husband visited the scene on Wednesday evening, and was seen comforting people. Singer Rita Ora also pitched in, helping to sort donations outside the tower.
Photographs and messages in English and Arabic have been left for loved ones.
Alongside them are words of anger and calls for justice, with people saying their safety concerns were not listened to.
The local authority - Kensington and Chelsea council - said 44 households had been placed in emergency accommodation so far.
Through the night, people donated food, clothes and blankets for those left without homes.
By early morning some volunteers said they were overwhelmed with donations and were turning people and vans away.
One volunteer, Bhupinder Singh, said: "It is times like this that the best of our community comes out. This is where you find out how good it is to be a Londoner."
Questions have been raised about why the fire appeared to spread so quickly and engulf the entire building.