Pembrokeshire has been in mourning this past week after one of the worst tragedies the county has seen in recent years.

An explosion at Chevron Oil Refinery, Pembroke, killed four people and seriously injured a fifth last Thursday evening.

Nearby properties were rocked by the blast shortly before 6.30 pm and huge plumes of black smoke could be seen billowing above the refinery for miles around.

On Monday, all employees and contractors at the refinery gathered in their work teams for a stand down through the morning.

At 11 am, all Chevron facilities in the UK observed a four minutes silence, one minute for each of the colleagues, Julie Jones, aged 54, a mother of one and a grandmother of one, from Pembroke; Dennis Riley, aged 52, a father of two and a grandfather, from Milford Haven; Robert Broome, aged 48, a father of seven from Milford Haven; and Andrew Jenkins, aged 33, a father of young twins from Milford Haven.

A fifth casualty remains in a critical, but stable condition in hospital.

The family have asked police not to release the name or any other details at this stage.

Since the incident, specially trained officers have also been supporting the families and next of kin of those who tragically lost their lives.

A book of condolence has also been opened within the refinery.

Independent counselling services were brought in by Chevron onto the site immediately after the incident.

Chevron say the explosion occurred while a storage tank was being taken out of service for maintenance.

A statement issued on Monday said: "The details of the incident will form the focus for the investigations, which have already started. The fire was brought under control very quickly by our own on-site fire service, together with Pembrokeshire command of the Mid and West Wales Fire and Rescue Service, and we are extremely grateful for their professionalism and speed of response. "

Gold Commander of the incident from Dyfed Powys Police, Chief Superintendent Gwyn Thomas, said: "Mid and West Wales Fire and Rescue Service received a call at 6.22 pm reporting an explosion at Chevron Oil Refinery.

"Five fire appliances were mobilised immediately (two from Pembroke Dock; two from Milford Haven and one from Tenby).

"Specialist fire appliances were also mobilised, including two foam vehicles, a chemical incident unit, a high volume pump from Pembroke Dock, environment unit from Pembroke Dock and a control unit from Carmarthen.

"The fire was the result of an explosion in a 730 cubic metre storage tank whilst maintenance work was carried out. Damage was also caused to an adjacent storage tank."

Assistant Chief Fire Officer Chris Davies said: "Crews from Mid and West Wales Fire and Rescue assisted the on-site Chevron fire personnel throughout the operation. The fire itself was extinguished quickly and the crews worked to make the scene safe for police to start their investigation.

"We can confirm that any materials released into the atmosphere as a result of the blast were immediately dispersed. The wind was blowing offshore, away from residential areas. Members of the public can be reassured that there is no ongoing risk to health as a result of the incident."

Chief Superintendent Gwyn Thomas continued: "A police investigation is now underway, with the Health and Safety Executive, and early indications show that this was a tragic industrial incident.

"Police officers have secured the scene and colleagues from Mid and West Wales Fire and Rescue are working to make the site safe to enable a multi agency investigation into the cause of the explosion to commence."

Greg Hanggi, refinery general manager, said: "This news is utterly devastating. The loss of our co-workers has come as a huge shock to us all. Our thoughts and deepest sympathy go out to their families. We will ensure that all employees and contractors are fully supported throughout this difficult time.

"We will take every step possible to determine the series of events that led to this tragic incident and ensure that any lessons learnt from it will be integrated into the business and shared with our industry partners.

"I would like to thank all the on-site responders and emergency service personnel for the dedication and professionalism they showed throughout this incident."

Senior Chevron managers from the US, including the president of Global Manufacturing, have been visiting the site this week to provide support to everyone at Pembroke.

Prime Minister expresses sympathy

Prime Minister David Cameron has expressed his deepest sympathies for the families of those killed in the Chevron blast last week.

In response to a question from local MP Simon Hart, Mr. Cameron called it a 'tragic incident' and paid tribute to the local community.

Mr. Hart asked Mr. Cameron at Prime Minister's Questions if he would endorse the safety record of Chevron and its new owner Valero in what can be a dangerous industry.

"The company has had a good safety record, and in an industry in which there are inherent risks," agreed Mr. Cameron.

He said he believed that there would be lessons to be learned from the incident and added that he would be happy to discuss the issue with Mr. Hart.

Huge wave of support

From across Chevron worldwide, all the major Milford Haven industrial sites and the local community in Pembroke, Chevron says it has received a huge number of messages of condolence and offers of support, for which the are extremely grateful and touched.

A statement from Chevron said: "Our focus over the coming days and weeks will be to work together to ensure that everyone on site receives the support they need from those around them.

"We would like to thank everyone at the refinery who responded to the incident, as well as the members of the emergency services. Also, we must recognise the continued support we are receiving from the local wider community."

Local reaction to the tragedy

Thursday's tragic explosion at Chevron has shocked and saddened the whole county, with tributes pouring in from around the nation. Here are some of the tributes which have been received:

CLR. JOHN ALLEN-MIREHOUSE

The deputy leader of Pembrokeshire County Council, Clr. John Allen-Mirehouse, who is also the local member, commented: "We are all deeply shocked and saddened by this awful accident and, on behalf of the county council and, I am sure, everyone in Pembrokeshire, I extend our deepest condolences to the bereaved families and everyone involved.

"It always seems particularly tragic when people set off to work as normal and then never come home.

"As the local county councillor, I have regular dealings with the refinery and I know that the management and staff are absolutely devastated.

"I have also seen at first hand the company's total commitment to safety. Refining is an inherently dangerous operation and it is tribute to the high standards set, that incidents like this are mercifully rare. I know they will be as determined as anyone to discover what caused this terrible explosion.

"We must remember how important this refinery is to Pembrokeshire. It is one of the cornerstones of the Welsh economy. Not only does it provide around 1,400 well-paid jobs and about £40 million to the local economy, but it contributes massively to the Treasury in taxes."

MP SIMON HART

South Pembrokeshire MP Simon Hart said: "My thoughts are with the bereaved families and those who are injured. For four people to die in one industrial accident in Pembrokeshire or anywhere else is shocking.

"We live alongside these industrial giants that provide so much work for the county and few of us think of the risks that come with working there.

"I am assured that a full investigation will be taking place and I have been in touch with the refinery's general manager to make sure that I am kept fully up to date with that process."

AM ANGELA BURNS

Angela Burns Assembly Member for South Pembrokeshire, said: "I was in contact with Chevron during the night as the details of this accident emerged and was deeply sorry to hear of the loss of life. This is a personal tragedy for the four families who have lost a beloved person and our thoughts and prayers must be with them and the family of the fifth man who is still so very ill in hospital.

"The emergency services and the Gold command structure acted impeccably in their response to the events of the night and I would like to thank the fire fighters, the police, the ambulance crews and of course the staff at Chevron for acting so swiftly and for ensuring that the planned procedures and emergency protocols were implemented and that the explosion was contained and extinguished as quickly as it was.

"Obviously, the causes of this terrible accident are unclear and I have been very uncomfortable about some of the rumours and speculation that are circulating.

"I welcome the inquiry being conducted by Chevron and I know that the police, health and safety and the Environment Agency will be conducting inquiries of their own.

"What is crucial is that we understand exactly what happened, learn from and implement any lessons that we can and also ensure that those lessons are communicated to the wider sector so that we can have the best possible practice in all of the energy industries based on the Haven.

"This is the time for us to stand shoulder to shoulder with the families involved and with the staff and contractors at Chevron.

"We have always been proud of the highly skilled workforce we have there and of the value that Chevron has contributed to the local economy and to many community projects over the years.

"I believe it is possible for us to do that whilst at the same time conducting a thorough and probing investigation into what happened to ensure that the best possible procedures and practices are in place to protect us all."

MAYOR OF PEMBROKE

The Mayor of Pembroke, Clr. Aden Brinn, expressed his deepest condolences on behalf of Pembroke Town Council and residents of Pembroke to the families and friends of the victims of this tragic incident.

Special thanks are also extended to members of the emergency services for their professional response. As a token of respect, the Union flag is being flown at half mast at Pembroke Town Hall.

PEMBROKE DOCK TOWN COUNCIL

Pembroke Dock Town Council would like to send their condolences and deepest sympathy to the families, friends and colleagues of the deceased, and their thoughts are with those injured in the tragic accident.

They would also like to thank and praise the emergency services for their quick response in dealing with a dangerous situation.

CHURCH LEADERS

Church leaders joined in extending their sympathies and condolences to the families affected by Thursday's refinery explosion.

The Archbishop of Wales, Dr. Barry Morgan, and the Bishop of St. Davids, Rt. Rev. Wyn Evans, issued a joint statement expressing their sympathies and extending condolences to the families and colleagues of the four contractors who died.

"Our prayers also go out to the fifth victim of this terrible tragedy, in the hope that he will make a full recovery from his injuries," the statement says.

Bishop Wyn spoke about the incident when he fulfilled a long-standing engagement at Warren Church, which is close to the Chevron refinery. The bishop led a service celebrating the 50th anniversary of the German presence at the Castlemartin artillery ranges.

FIRST MINISTER

CARWYN JONES

First Minister Carwyn Jones said: I am shocked to learn of the accident at the Chevron refinery in Pembroke. My sincere condolences go to the bereaved families and colleagues."

The First Minister is being kept fully informed of developments.

JOYCE WATSON AM

Joyce Watson AM said: "This accident has come as a shock to people across Pembrokeshire, and across Wales. The Chevron refinery plays a huge role in our local economy, and many people will have personal connections with it. My thoughts and sympathies are with the families and the colleagues of those who lost their lives, and of the worker who is being treated for serious injuries.

"I must praise the work of our brave emergency service workers who attended the incident. I am keen to be updated on the investigation into the incident, to understand how this occurred and to be sure that any lessons will be learned.

"The investigation is at a very early stage, but should matters arise which the Welsh Government can act on, I will of course seek to raise those in the Assembly."