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 by witnesses as like “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 is in place around the site, with acetylene and liquid gas cylinders along with kerosene in the wreckage.
Alex Waller, the Cheshire fire service’s head of service delivery, added: “Our thoughts are with the families of the missing. At the moment we are really doing all we can.
“We have been working around the clock, overnight, we have not scaled back resources and we are not going to do so.
“We are going to keep going until we find or locate any casualties or any people.
“As you can see it is really difficult, really challenging, really dangerous.
“We are painstakingly moving through all of the wreckage, the search and rescue teams they will pull back any wreckage, we have got heavy lifting gear, we will pull that back, very very gently and see if we can find anybody underneath.
“We also have to bear in mind there’s an investigation, so there’s a lot of photography going on at the same time, imagery, any voids within that pile, where somebody would have a chance.
“The dogs will search an area, then we move in, and slowly peel the debris away.”
Tony Brown, a station manager with Merseyside Fire and Rescue Service, but acting as a search and rescue expert adviser, said the process was “slow and steady”.
“We have got a rough idea of where the people are, from intelligence before the incident and from running the search dogs over the pile. We are not going to give up, in the hope we do find somebody.”
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.
David Rutley, Conservative MP for Macclesfield, said: “There is still hope. Speaking to the chief fire officer obviously they are still treating this as a search and rescue, so we hope and we pray. But given the scale of the explosion, clearly the probabilities are not the best but we still hope.
“And all I can say is having been down to the scene of the incident the fire and rescue operations are doing everything they can to find these people and dowse down the fire so they can get the search and rescue teams in as soon as possible.
“There is an amazing amount of work gone in to try and find these people, so I can’t think of anything more they could have done, so let’s just hope now that they can get that job done quickly.”
Mr Rutley said the village of Bosley had a population of around 400 and the mill’s 50 workers made it the biggest employer in the village.
He added: “There are some very important questions that local people in the village want to get answers to. I want to make sure, along with all the other services, particularly the Health and Safety Executive, that those questions get answered.
“Certainly people have been in touch with me about environmental concerns because there has been a lot of sawdust in the air, but that was more an environmental basis and I know that the council have been on to that, followed up rigorously on those issues.
“I understand that there have been fires there before but again that hasn’t been brought to my attention until what happened tragically yesterday.
“But all of these things need to be put together and then, particularly the cause of what happened here, to work out how on earth this tragic accident could have happened.
“So there certainly are questions that need to be answered but I think that comes after today and once we have been able to hopefully find those people unaccounted for.”