The search is continuing for three missing workers feared killed when a blast ripped through a wood flour mill.
One body has been recovered from the wreckage in the village of Bosley, Cheshire, where a 1,000C inferno reduced the four-storey building to rubble, but so far it has not been positively identified.
Fire and rescue teams have been working non-stop to find William Barks, 51, Dorothy Bailey, 62, Jason Shingler, 38, and Derek Moore, 62, since Friday's explosions and fire.
Paul Hancock, Cheshire's chief fire officer, suggested there was little hope of finding any survivors when he said officers were heading into a search and recovery phase rather than search and rescue.
He said: "The current focus is in a particular area about five metres by five metres and we are currently excavating that particular area.
"We are now approximately three metres down into that excavation with a potential further 10 metres to go. So it's a significant challenge.
"The area is where the body was recovered.
"We are probably now moving into a search and recovery phase rather than a search and rescue phase.
"It is going to take a long time. This is a challenging environment for all the emergency workers down at the scene and they are working exceptionally hard to retrieve the three missing individuals."
In a statement, the mill's bosses, Wood Treatment Limited said: "We are shocked and saddened by the incident at our mill in Bosley and our thoughts and sympathies are with everyone affected and their families.
"The mill has been part of the community in Bosley since 1927 and we take the safety of our employees extremely seriously.
"We are committed to establishing the cause of this incident and we will continue to co-operate fully with the emergency services and Health and Safety Executive. However, we feel it would be inappropriate to comment further at this time while investigations are ongoing."
The family of one of the missing workers said they were "very, very angry" at the alleged lack of sympathy from the mill's owners, saying they had not been in touch with them since the blast.
Kelvin Barks, brother of William Barks, told ITV News: "My brother worked at that mill for 12 years. He's been missing for over three days now. In all that time nobody at the company has contacted us at all. No offer of support or sympathy or help."
Guy Hindle, assistant chief constable of Cheshire Police, said identifying the recovered body and establishing the cause of the blast would also not be quick tasks.
Three Health and Safety Executive (HSE) officers are working at police headquarters with the major investigation team, he said.
He added he did not share "disquiet" voiced by some around the wood mill owners' involvement with the investigation.
He said: "The company has not been in touch with the families because they have been unable to do so.
"They have not been reticent or unwilling to do so. The company are working with us to seek to establish the cause of the explosion and the fire."
The HSE served Wood Treatment Ltd with improvement notices two years ago in which it warned of a risk of an explosion or fire, although the company complied with the notice.
The firm was told: "You have failed to ensure that the risk from fire or explosion involving LPG stored in your two bulk tanks at the side of the Station Shed North at your premises at Tunstall Road is either eliminated or reduced, so far as is reasonably practicable."
It added that the tanks "are not protected by suitable barriers to minimise the risk of damage from vehicle impact; the concrete path has not been fitted with suitable barriers to prevent falls; and combustible materials are stored within the separation distance".
Enforcement officers from Cheshire East Council were on the site two weeks ago to make sure the firm cleared the area after complaints of sawdust. The site was also struck by two fires, in 2010 and 2012.