TWO workers were killed yesterday in an explosion at a steel plant in Cardiff in which four more were injured.

The unnamed workers were initially pronounced missing after a “deafening” blast at Celsa UK’s site near the city centre at 10.30am.

Their family, friends and colleagues’ worst fears were confirmed later by the police who found their bodies at the site.

The injured workers were being treated for trauma and “minor injuries” at the University of Wales Hospital in Cardiff, where a major incident was declared.

A fifth person received treatment at the scene.

First Minister of Wales Carwyn Jones said he was “deeply saddened” by the worst industrial accident in the country in recent memory.

Local Labour MP Stephen Doughty called it a “dark day in the proud history of steel-making in Cardiff.

“I am devastated to learn that two people have tragically lost their lives as a result of the serious incident at the Celsa steel works in my constituency this morning,” he said.

More than two dozen ambulances and fire engines were deployed to the scene, along with the air ambulance.

One man working at a nearby site said: “There was a massive bang. We all felt the floor shake. It was very worrying seeing lots of ambulances and fire engines go in there.”

Ian Greenman of South Wales Fire and Rescue Service said: “Our crews worked tirelessly, but despite heroic efforts we were unable to save two people.”

Steel union Community reported that the explosion came from the rod and bar mill and may have involved an oil accumulator in the basement of the building.

General secretary Roy Rickhuss said: “This is absolutely tragic news and our immediate thoughts are with the families and colleagues of those who died and those who were injured.

“Lessons will need to be learnt from what happened so that this cannot happen again, but for today we should be focused on supporting everybody affected.”

A Health and Safety Executive representative was at the site, although investigations currently are being led by the police.

Nine people were killed at work in Wales last year, the third highest rate of any area of Britain.