Chevron names four killed in Welsh blast
Riley, 52, was a grandfather and Robert Broome, 48, had seven children. Jenkins, 33, was the father of young twins.
Dyfed Powys Police said a fifth person, who has not been named, remained in a critical but stable condition in hospital last night.
A joint police and Health and Safety Executive investigation is being carried out into the blast that tore through the refinery in Pembroke Dock, South Wales.
It is believed the explosion may have been a "tragic industrial accident". Maintenance work had been carried out on a 730 cubic metre storage tank which exploded at around 6.20pm on Thursday, damaging an adjacent vessel.
Local Tory MP Simon Hart said he has been assured there will be a "full investigation". He added: "We live with these industrial giants that provide so much work for the county, and few of us think of the risks that come with working there."
Local residents, many of whom said they were shocked by the incident, said that some risk was inevitable at industrial sites, with one describing the refinery as a "time bomb".
Another, Bronwen Lewis, said: "There will always be accidents wherever you have a big place like this."
It is believed it could take several weeks to establish the cause of the blast.
Detective Chief Inspector Martin Davies, the senior investigating officer, said: "Since the incident occurred, our specially trained officers have been supporting the families and next of kin of those who tragically lost their lives. 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, and the media are kindly asked to respect the privacy of all the families affected by this incident at this difficult time."
Chevron said it would carry out its own investigation, adding that the company's thoughts were with the families of those who had died.
In a statement, the company said: "Chevron is hugely saddened by the death of four of its contractor colleagues and our thoughts go out to their families at this very difficult time.
"One contractor colleague remains in hospital, where he is still receiving treatment.
"Pembroke refinery is a very close family and this tragedy has been a great shock to everyone."The welfare of our employees is our key priority and we are providing counselling support to all our staff and their families."
A nearby construction site where a power station is being built was shut on Friday as a mark of respect.