A massive explosion was reported in southwest England on Thursday, at a warehouse in Avonmouth near Bristol. The large explosion is said to have caused multiple casualties, but no further details are available on what triggered the explosion. According to Reuters, the blast took place at a water treatment site, which killed four workers - three workers at Wessex Water and fourth a contractor.

South Western Ambulance Service was rushed to the site, where witnesses said the "loud explosion shook buildings."

"South Western Ambulance Service is responding to a serious incident at premises on King's Weston Lane, Avonmouth, Bristol. We have attended with multiple resources alongside fire service and police personnel," the ambulance service statement said.

Photo by camilo jimenez on Unsplash

Confirming the deaths, Chief Inspector Mark Runacres of Avon and Somerset Police told reporters that "despite the best efforts of all those involved, we can confirm that there have been four fatalities." One more person is believed to be injured, but not in a life-threatening condition.

Emergency services attending to the serious incident include police cars, fire trucks and a helicopter. Photos from the scene show a damaged tank.

Prime Minister Boris Johnson said he was deeply saddened to learn about the deaths and thanked the emergency response team for their efforts.