Detectives investigating the Grenfell Tower fire said the official number of presumed dead "will be higher" than the current figure of 58 as they released new images showing the scale of devastation inside the building.
In a statement, Commander Stuart Cundy said the scale of the "indescribable" damage from the fire was such that some of the victims may never be identified.
The revised figure will be released on Monday.
Mr Cundy said it was already clear that the total number of the dead "will be higher" than the figure previously given by police but said he would not "speculate" on a figure.
"Whilst our teams have been from the bottom to the top of the tower, we must now carry out a full forensic and systematic search," he said.
"The conditions due to the fire damage verge on indescribable, which is why this will be such a lengthy operation taking weeks to complete."
"We must also prepare people for the terrible reality that some people may not be identified due to the intensity of the fire."
The force released new images and footage from inside the gutted building on Sunday that show the extent of the damage and highlight the challenge facing search teams.
The acknowledgement of the increased death toll will be welcomed by many survivors and families of victims, who have said that it is clear the number of those who perished is far higher than the figure previously given by police.
Mr Cundy stressed in his statement that he would not confirm deaths unless he could be sure that his reports were accurate.
It came as the London Mayor Sadiq Khan said the fire was a "preventable accident"caused by years of "mistakes and neglect" from officials.
Downing Street has also announced that every family who lost their home in the fire will receive cash payments of at least £5,500 as ministers seek to quell criticism over the response the the disaster.
The images released have been taken inside flats where police know that everyone inside has been accounted for a resident of each flat notified by police of the release of the material.
The material was captured by a specialist police recovery team who has been working closely alongside colleagues from the London Ambulance Service and the London Fire Brigade as part of the ongoing operation.
Mr Cundy appealed for anyone who knew about people who were living or may have been living in the tower at the time of the fire to make contact with police.
"We are not interested in your reasons for not telling us sooner, we just want to understand as best as we can who may still be inside the building," he said.