Two companies will face prosecution over a storage tank explosion at a Pembrokeshire oil refinery in 2011 which killed four people.

The four people - Dennis Riley, Robert Broome, Andrew Jenkins, and Julie Jones, were killed when a 160, 578-gallon (730,000 litres) storage tank exploded, damaging a vessel next to it, whilst another employee, Andrew Phillips, was also seriously injured in the blast.

The Health and Safety Executive (HSE) have announced that they will now bring charges over the Chevron Pembroke Refinery explosion: “Valero Energy UK Limited and B & A Contracts Limited are to face charges under Sections 2(1) and 3(1) of the Health and Safety at Work etc Act 1974.

“At the time of the incident the refinery was operated by Chevron Limited, but ownership changed in August 2011.”

The defendants are due to appear at Haverfordwest Magistrates’ Court later this year on September 24 at 2 pm.

HSE’s deputy director field operations, Jane Lassey, said: “Following a painstaking and extremely thorough investigation, much of which was conducted jointly with Dyfed Powys Police, we have concluded that there is sufficient evidence to bring criminal charges.”

A spokesman for Valero, said: “We can confirm we have been informed that the Health & Safety Executive is to bring proceedings against Chevron in relation to the incident at Pembroke Refinery in 2011.

“Valero itself is named as a party to the proceedings simply because of its subsequent acquisition of the refinery.”