Three Wessex Water employees and a contractor have died after a large explosion at the company’s treatment site at Avonmouth near Bristol.
Police said a fifth person was also hurt but their injuries are not believed to be life-threatening.
Chief inspector Mark Runacres said: “A thorough investigation will be carried out into what happened today, involving a number of agencies and the health and safety executive in due course and we will not be speculating on the cause of the explosion while such work is being undertaken.
“What we can confirm though is this is not being treated as terror-related incident. The explosion happened in a silo that holds treated biosolids before it is recycled to land as an organic soil conditioner. I can reassure people living in the nearby area that there is not believed to be any ongoing public safety concerns following today’s events.”
Wessex chief executive Colin Skellett said: “We are absolutely devastated that the tragic incident at our site earlier today has resulted in four fatalities.
“Our thoughts are with the families, friends and colleagues of those involved.
“We are working with the Health and Safety Executive to understand what happened and why.”
Avon Fire and Rescue Service were called to the site at 11.22am today (3 December) after reports of a large explosion in a warehouse.
A spokesperson for South Western Ambulance Service said: “We sent multiple resources to the scene, including land, air and other specialist paramedic teams.
“We supported Avon Fire & Rescue Service and Avon & Somerset Police at the scene.”