A third body has been recovered at the Bosley Mill site in Cheshire, following an explosion last week.
Police say search teams made the discovery after several silos at the wood flour mill were removed yesterday.
Sky News correspondent Mike McCarthy, who is at the site, says the silos were causing problems because they were over-heating and having to be hosed down.
The news came as relatives of those killed in the blast prepared to visit the site.
"For their own reasons (the families) would like to see the level of activity ... to search for the missing people, and also to pay their respects and understand the nature of the scene," Assistant Chief Constable Guy Hindle said.
"That'll be a difficult time for them all."
A series of explosions destroyed the mill, owned by Wood Treatment Ltd, on Friday and emergency services have been searching for three men and one woman unaccounted for.
They have been named as William Barks, 51; Dorothy Bailey, 62; Jason Shingler, 38; and Derek Moore, 62.
Police have not yet confirmed the identity of the third body.
The brother of Mr Barks yesterday paid a tearful tribute to a man he described as "so happy" and "so clever".
An investigation is under way to find out what caused the explosion.
It has emerged there were two previous fires at the site in 2010 and 2012 and there were recent complaints about sawdust and noise.
Cheshire Police now has aerial footage of the controlled operation to bring down the silos that had been identified as being a risk to the search and rescue operation.