A large blast in a warehouse near Bristol in England has caused multiple casualties, a spokeswoman for the fire brigade said on Thursday.

The fire service had previously said on Twitter that it was responding to an incident after being called to a large explosion in Avonmouth, south west England. It said it had been joined there by the police and ambulance.

“We can confirm there are multiple casualties on site," a spokeswoman for Avon Fire and Rescue Service said, adding that injuries were serious. "It's very much ongoing," she said.

The explosion took place at a waste treatment facility for the nearby city of Bristol, the spokeswoman added.

The fire service said it had been joined there by police and ambulances.

A police spokeswoman said they were searching the location to make sure everyone was accounted for, but had no details of casualties.