AN explosion at a waste water treatment works near Bristol that has caused multiple injuries and four confirmed casualties is believed to be linked to its chemical tanks, police said today.

A major incident was declared at Wessex Water’s Bristol water recycling centre in Kings Weston Lane, Avonmouth, after reports of a “large explosion” at 11.22am.

Avon and Somerset Police said inquiries were ongoing into the exact cause of the blast.

A spokesman said: “An explosion is believed to have occurred involving one of the chemical tanks.

“A rescue operation was subsequently led by the fire service, involving five appliances and two turntable crews, and we can confirm there have been a number of casualties.

“A full investigation into the incident will be conducted.”

Avon Fire and Rescue Service said crews from eight stations were mobilised to respond to the incident and confirmed there had been “multiple casualties on site.”

Bristol North West Labour MP Darren Jones said: “This is a serious incident and my thoughts are with those workers who have injured on site today.

“I’m grateful to our fire, police and ambulance staff for their quick response.”

Unite regional secretary for the south west Steve Preddy said: “We can confirm that Unite has three members working at Wessex Water Services Ltd in Avonmouth. 

“We have contacted them this afternoon and they are, thankfully, uninjured, although in a state of shock. 

“Unite will be giving our members maximum support in the days and weeks ahead.

“Unite the union would wish to extend its deepest sympathy to the families of those employees who have lost their lives and as well as those injured in the explosion – our thoughts and solidarity are with all those affected by this tragic event.

“Unite would also like to thank the emergency services for their rapid, brave and professional response to this major incident.

“There will, in due course, be an investigation into this incident and Unite will contribute to any such inquiry.”