The search for survivors after an explosion and fire at a mill in the UK is moving into a "recovery phase", according to police.
Emergency services have been searching for three men and one woman following the blaze in Bosley, Cheshire, on Friday. One body has been recovered, but not yet identified.
The four have been named as William Barks, 51; Dorothy Bailey, 62; Jason Shingler, 38; and Derek Moore, 62.
Chief Fire Officer Paul Hancock said the search is expected to take a long time given the challenging conditions the teams are faced with.
"We are moving into a recovery phase rather than a search and rescue phase," he told a news conference.
He added that "we are still hopeful of potentially finding life as well" but acknowledged that four days after the blast hope was fading.
Mr Hancock said the search is focusing in the same place where the body was found on Sunday evening, a 5m by 5m area where the teams are excavating.
"We are now approximately three metres down into that excavation with a potential further 10 metres to go. So it's a significant challenge," he said.
The series of explosions ripped apart the wood flour mill and reduced the four-storey building to rubble.
Emergency services have been working non-stop to find those missing and extinguish the smouldering wreckage.
Six fire engines are at the site with fire crews and sniffer dogs, as two high volume pumps provide water to cool the site.
The owners of the mill were warned of a risk of an explosion two years ago, according to a March 2013 health service notice.
In it, Wood Treatment Ltd 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."
The notice said 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".
The company has not made any public comment since the explosions on Friday morning.
However, Assistant Chief Constable Guy Hindle defended the company, saying he did not share "disquiet" voiced by some over the wood mill owners' involvement with the investigation.
"The company have not been in touch with the families because they have been unable to do so," he said.
"They have not been reticent or unwilling to do so, and the company are working with us to seek to establish the cause of the explosion and the fire."
