Four men who died in an explosion at a waste water treatment works have been named by police.

Michael James, 64, Brian Vickery, 63, Raymond White, 57, and Luke Wheaton, 16, were killed in the incident in Avonmouth on Thursday.

Emergency services were called to Wessex Water’s Bristol water recycling centre following reports of a large explosion involving one of the chemical tanks at the site.

The blast happened in a silo that held treated biosolids before they are recycled to land as an organic soil conditioner.

Avon and Somerset Police said a cordon at the site was likely to remain in place “over the coming days” as an investigation into the cause of the incident was carried out.

This is being supported by the Health and Safety Executive (HSE) and a team of chemical and mechanical experts, the force said.

Superintendent Simon Brickwood said: “I’d like to extend my heartfelt sympathies to the families of those involved in yesterday’s tragic incident.

“An investigation has been launched into the causes of the explosion, with the support of partner agencies and the Health and Safety Executive.

“This is likely to be ongoing for some time and we will be keeping the victims’ families informed throughout.

“We appreciate the impact this incident has had on the local community and we thank those affected for their patience while our investigative work is carried out.

“The local neighbourhood policing team is available to address any concerns members of the public may have.

“I’d like to pay tribute to those involved in the emergency response, who have been at the scene throughout the night under very difficult and challenging circumstances.”

Specially-trained officers are supporting the family of the four men who died in the incident.

Formal identification is yet to take place and post-mortem examinations are under way, a force spokesman said.

A fifth person who was injured in the explosion is now at home and investigators will speak to them when appropriate.

Giles Hyder, HSE’s head of operations in the South West, said: “We send our deepest condolences to the families of those who tragically died. It is important a joint investigation is carried out.

“We will provide specialist support to what is likely to be a complex investigation under the command of the police.”

On Thursday, Avon Fire and Rescue Service described the scene of the incident as “very challenging”.

Search and rescue dogs were used to identify casualties following the blast.

The explosion is not being treated as terror-related and there are not believed to be any ongoing public safety concerns.

Colin Skellett, chief executive of Wessex Water, said: “We are all absolutely devastated by what has happened.

“Our hearts go out to the family, friends and colleagues of those who lost their lives during the tragic event on Thursday.

“I know from the thoughts and comments I have received from so many, that this has affected the whole Wessex Water family.

“I know Avonmouth, I worked there for many years, and I know the people, some of whom have lost their lives during this terrible incident.”