Hope is fading for four workers missing after two huge explosions and a fire destroyed a mill.
Search and rescue teams are now preparing to enter the dangerous site of twisted metal and rubble still smouldering after the incident at the wood flour mill in the village of Bosley, Cheshire.
The four still missing, three men and a woman, were believed to have been in the building and near the seat of the explosion that ripped through the mill at around 9.10am yesterday.
Paul Hancock, chief fire officer for Cheshire Fire and Rescue Service (CFRS) said: "There's still hope but the longer the incident continues without knowing or locating these four individuals, it is looking more like a recovery than a rescue operation. Until we account for them there's always hope."
At first light today, around 5am, an initial assessment was done of the site, with around 20 firefighters forming a specialist urban search and rescue team, preparing to start to enter parts of the site using a sniffer dog.
Sixty other firefighters along with ambulance crews and police are on hand with water still being used to douse and cool silos and thermal image cameras assessing temperatures to look for "hot spots".
Mr Hancock said the four storey building was completely destroyed in the incident, starting with an explosion, followed by a much larger explosion, described as witnesses as "an earthquake" followed by fire engulfing the site as massive plumes of flames shot 70 metres high.
He said: "There's been an explosion. The building has burst from the inside and because of the subsequent fire it has collapsed in on itself which has created a number of voids.
"So we remain hopeful but remain realistic that it is looking more like a recovery operation than a rescue operation."
A one-mile cordon remains in place around the site, with acetylene and liquid gas cylinders along with kerosene in the wreckage.
Mr Hancock said the next few hours will be a "slow, methodical process" of creating safe zones on the site for firefighters to search for the missing workers.
Cheshire Police said they were working closely with the families of the four missing but were not releasing names. All four are believed to be local, with one from the village of Bosley.
A total of 35 casualties were assessed at the scene, with four people taken to hospital.
A 29-year-old woman was airlifted to Queen Elizabeth Hospital, Birmingham, after she suffered serious burns and blast injuries to her head, face, arms and chest.
Another two people were taken to a specialist trauma unit at Royal Stoke University Hospital, while a fourth male casualty was taken to Whiston Hospital, Merseyside.
Up to 80 firefighters from Cheshire, Derbyshire, Greater Manchester and Staffordshire fire and rescue services attended and were supported by colleagues from the West Midlands and North West ambulance services, together with Cheshire Police.
The cause of the blaze is under investigation. The mill, which made linoleum products out of wood ground down to a powder or flour, is run by Wood Treatment Ltd, part of the Bodens Group, which says the company has been producing wood flour since 1930 and is the sole manufacturer in the UK, according to the Bodens Group of Companies website.
The site suffered a fire in 2012.