A number of casualties are being reported as UK emergency fire and rescue crews deal with what has been described as a large explosion at a waste waterworks in Avonmouth near Bristol in south-west England on Thursday.
The blast is believed to have involved one of the chemical tanks at the Wessex Water recycling centre and the local Avon and Somerset Police said that a "major incident" has been declared.
It said that a rescue operation was led by the fire service, involving five appliances and two turntable crews, and it can be confirmed that there have been a "number of casualties".
The police force said that a full investigation into the incident will be conducted.
"Officers remain at the scene and are likely to be for some time as we work together with other agencies in dealing with this major incident," said Chief Inspector Mark Runacres.
"A cordon has been set up and we'd advise members of the public to avoid the area at this time where possible to allow the emergency services to carry out their work. Police enquiries into exactly what happened are at a very early stage and are continuing," he said.
Photos from the scene showed police cars, fire trucks and a helicopter in attendance and other images appear to show a damaged tank and what looks like smoke rising from behind a mound.
Witnesses reported hearing a "very loud explosion" that "shook buildings".
"We sent multiple resources to the scene, including land air and other specialist paramedic teams," a spokesperson for South Western Ambulance Service said.
Bristol Waste, which runs the nearby Avonmouth recycling centre, tweeted it had closed the site temporarily.