Police fear they may never identify all of those killed in the Grenfell Tower disaster.
Six bodies have so far been recovered from the gutted 24-storey tower, while 11 have been located inside but cannot yet be removed.
Of those 17 people known to have died, six have been provisionally identified, but the death toll is expected to rise significantly.
Metropolitan Police Commander Stuart Cundy said: "It may be - and I just don't know - it may be that ultimately some victims remain unidentified. I won't know that until we've gone through the full recovery from Grenfell Tower and we know exactly what we've got and I anticipate that is going to take a considerable period of time.
"Not just the immediate recovery of the bodies we have found but the full search of that whole building, we could be talking weeks, we could be talking months - it is a very long process. There is a risk that sadly we may not be able to identify everybody."
Prime Minister Theresa May ordered a full public inquiry into the disaster amid mounting anger that the fire might have been preventable.
Labour leader Jeremy Corbyn also visited the area, and comforted residents at St Clement's Church, where shelter and support was being given to people affected by the fire.
Speaking to reporters, commander Cundy's voice at one stage cracked as he revealed the emotional toll of the events.
Asked if the death toll could climb to triple figures, he said: "For those of us that have been down there, it's pretty emotional, so I hope it is not triple figures, but I can't be drawn on the numbers."
In other developments:
A criminal investigation has been launched, after calls for those involved in the building's recent renovation - which many claim posed a major safety risk - to face prosecution.
"We as the police have started an investigation, I mentioned when I was down at the scene this morning that one of our very senior investigating officers is leading that for us," the commander said.
"I am not saying there are criminal offences that have been committed, that's why you do an investigation. This will need to be a lot of work between us and other investigating agencies to establish what has happened and why and that is going to take a considerable period of time."
The fire was initially extinguished shortly after 1am - 24 hours after the first alarms - paving the way for searches in Grenfell's worst-affected areas. But the blaze flared up again yesterday afternoon, forcing search teams to scale back their efforts.