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."