The Bosley mill incident which has killed at least three people is the worst rescue crews have seen for a decade.
Paul Hitchen, from Urban Search and Rescue, said: "The scale of the incident is unprecedented in this country in the last 10 years.
"It's extremely dangerous and arduous for the rescuers. There's a massive amount of metal, concrete and brickwork which we need to move to continue the search.
"The priority is the rescue of the casualties. It's not possible to say yet when we will find the fourth body."
Structures at Bosley mill are being knocked down as the site is cleared.
This video footage released by Cheshire Police shows a silo, which is commonly used to store grain, being demolished.
Three bodies have been found and one worker is still missing following two explosions at the mill last week.
The owners of Bosley mill have released a statement speaking of their "devastation" at the loss of at least three colleagues.
It comes nearly a week after the tragedy happened during which time the families affected say they have had no contact from Wood Treatment Limited.
The statement said they had now contacted all four families involved and are "discussing how best" to help them.
It added: "They were all highly valued members of staff and our thoughts and deepest sympathies are with their families at this difficult time.
"The mill has been part of village life in Bosley for almost 90 years and we share the pain of the community.
"Our primary focus remains supporting the families of those affected, our employees and the local community as best we can while our site and facilities remain closed.
"We are absolutely committed to establishing the cause of this incident and will continue to co-operate fully with the emergency services and Health and Safety Executive. Company staff have been on site since last Friday assisting the authorities.
"We take the safety of our employees extremely seriously but it would be inappropriate to speculate about the circumstances of this incident until the full investigation is complete."
The brother of one of the four people killed in a mill explosion in Cheshire last week has laid flowers at the site in tribute to his sibling.
Kelvin Barks laid the flowers for his brother William together with a poster saying "R.I.P Will Barks. You are our world."
ITV News Correspondent Damon Green is at the scene:
A third body has been found at the Cheshire wood flour mill destroyed in a huge explosion last week.
Cheshire Police said they found the body, which has not been identified, at the Wood Treatment Limited plant in the village of Bosley after they removed three silos yesterday.
A spokesman said: "This has directly allowed the search and recovery operation to continue work at a section of the site indicated previously by search dogs. This has led to the discovery of a third body."
The families of the four people killed in the blast are expected to visit the site today and pay their respects.
Police investigating the Bosley mill explosion have spoken to the owners of the company and employees that worked there in a bid to discover the cause of the blast.
Describing the site as a "potential crime scene", Cheshire Police said they were attempting to gain information on the history of Wood Treatment Limited, which operated the wood flour mill.
Families of the four people missing following the disaster will make a visit facilitated by emergency services tomorrow, police said.
The first body recovered from the Bosley mill fire wreckage is believed to be that of William Barks, Cheshire Police has said.
The 51-year-old, who had been married for 31 years, was born and bred in Leek, Staffordshire.
Police said the body, recovered on Sunday, did not belong to any of the other three people missing following the blast.
Identifications on a second recovered body are ongoing, it was added.
Earlier his brother told ITV News Barks was a "hero" who was "so knowledgable" and "well-respected by everybody".
Kelvin Barks also said the fire at the wood mill had been a "disaster waiting to happen", alleging that the owners had failed to buy parts for a faulty machine despite "relentless" requests.
Kelvin Barks told ITV News his brother William, who was an engineer at the factory, tried to get a new job but 'had bills to pay'.Read the full story ›
A Bosley mill worker says he was given no safety training whatsoever before he started working there just a week ago.
Scott Cole told ITV News: "There was no safety training at all.
"I went in there to have a brief interview, three minutes, and he told me to start on Monday.
"He didn't tell me how to work the machines, nothing. I just learnt myself. I asked for a protection mask. Three days in, and I still didn't get one."
The Health and Safety Executive is now investigating the causes of the explosion.
The mill owners have said they will cooperate with the process but families of four workers still missing said they were "disgusted" they had not been in touch since the incident happened.
Dorothy Bailey, Derek Moore, Jason Shingler and William Barks have been missing since Friday's explosions.Read the full story ›