Metropolitan Police Deputy Commissioner Craig Mackey said the “extraordinary size” of the potential crime scene meant those who worked in the aftermath of the Twin Towers disaster in 2001 were being called upon.
Mr Mackey said the 200 UK officers already working on the case were faced with sifting through 15 tonnes of debris on each of the building’s 24 floors.
It came as Scotland Yard confirmed the latest victim as 68-year-old Majorie Vital. At least 80 people are thought to have died in the devastating fire in north Kensington on 14 June.
Giving an update at the London Assembly Police and Crime Committee, Mr Mackey said: “This is one of the most complex recovery operations we've seen.
“The people we're taking advice from – which gives you an idea of the complexity – are some of the people who worked on 9/11 and the fall of the Towers.
“It is an extraordinary size of crime scene.”
Mr Mackey said it was necessary to call on US counterparts because of their experience in a “comparable” operation.
He said: “Without wanting to be too graphic – but I hope it helps explain – the fire in some parts of that building (Grenfell) burned at over 1,000 degrees for a considerable period of time.
“So we are now working through floor by floor and it is literally a case of sifting and working through the debris - sadly, the remains - to try and desperately identify parts of people so we can reunite (the remains with families).
“There’s about 15 tonnes of material to work through and we think we'll be working through until Christmas time in terms of working through that scene gathering all the evidence.
“We're working with everyone you'd expect to see.
“The role of disaster victim identification is actually something UK policing has built up a level of knowledge in over a number of years.
“The only comparable advice we can find is from the challenge that was 9/11.”
He said the investigation was “going to be one of the largest and most complex” in the Met's history, but added that he would be “guessing” if he had to put a timeframe on when any arrests might be made.
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