A large blast at a water treatment site on the outskirts of Bristol in England killed four people and injured a fifth, local emergency services said on Thursday. /VCG

Three of the dead were workers at Wessex Water, which operates the plant, while the fourth was a contractor. The fifth person injured is not in a life-threatening condition. /VCG

The blast occurred in a silo containing what Chief Inspector Mark Runacres of Avon and Somerset Police called "treated biosolids" intended for use as fertilizer. /VCG

Police said emergency services had contacted the victims' families, and that there was no connection to terrorism or any ongoing threat to people living nearby. /VCG

Police also said government health and safety officials would conduct an investigation into the exact cause of the explosion. /VCG

UK Prime Minister Boris Johnson said in a statement on social media that he was "deeply saddened" to learn of the deaths and thanked emergency services for their response. /VCG