Police declared a major incident after the explosion at Wood Flour Mills in the village of Bosley, near Macclesfield, Cheshire. Four people are believed to be trapped in the collapsed four-storey building.
Fifteen fire engines have been dealing with the aftermath of the explosions, and fire crews warned there was a risk of further damage. “There is a fully developed fire in several areas,” a spokesperson for Cheshire Fire and Rescue said.
“Firefighters are facing a dangerous situation as they cannot rule out further explosions. People are advised to avoid the area.”
A 29-year-old woman suffered serious burns and blast injuries to her head, face, arms and chest, West Midlands Ambulance Service said. She has been airlifted to Queen Elizabeth Hospital Birmingham for further specialist treatment, while two other people who suffered burns have also been taken to hospital.
One person was flown by air ambulance to Wythenshawe Hospital in Manchester, with the other taken to Royal Stoke University Hospital, the North West Ambulance Service said.
A further 35 people have also been assessed at the scene by ambulance staff but were not injured.
The explosions at the wood treatment works shook nearby homes and emergency services have warned local residents to close windows and doors because of smoke in the area.
Emergency crews were initially called to reports of an explosion at the site at around 9.10am. Cheshire Police confirmed later there had been a further two blasts.
A spokesman for North West Ambulance Service NHS Trust said: “Our primary role is to assess the level and nature of injuries, and ensure that those people most in need are treated first and taken to hospital.
“At this stage, it is too early for us to confirm the number of casualties.”
More than 40 pupils at Bosley Primary School, which is about a mile away from the explosion site, were being kept inside the school building with the doors and windows closed.