Black smoke billowed from the furnace

She said: "There was just one heck of a flash of flames, a sound of thunder my son started crying and saying, there is a fire.

"We are so used to seeing the flames and the smoke, but this was totally different it was just a mass of flames in between the houses."

Another nearby resident told how she could physically feel the heat from the flames on her face.

She said: "I could see it well above the roof tops....I thought the whole place was going to go up."

Meanwhile, workers at the plant have been describing the unpredictable nature of the steel-making process.

The scale of the explosion has obviously damaged the furnace itself

Arwel Fowler, Mid and West Wales Fire Service

Terry Mosley had been about to start work on the number five furnace when the explosion occurred.

He said: "As far as we know, it was just a maintenance day which involves working on the furnace and working on the stack.

"There are loads of things that can go wrong.

"It is a dangerous place to work, you have got to keep your eye on the gases, small explosions, fires and so forth... anything can go wrong."

After the explosion police sealed off the area and kept everyone well away from the site.

The first real knowledge of what had happened inside the works came from Assistant Chief Officer of the Mid and West Wales Fire Service, Arwel Fowler.

I arrived for work early and got here to be told that the number five blast furnace had blown out

Andrew Tutton, crane driver

He said: "There was a fire that was quickly extinguished.

"There were a number of subsidiary incidents as a result of the fires and they were dealt with as pockets of fires.

"The scale of the explosion has obviously damaged the furnace itself."

Andrew Tutton, a crane driver on the site, was one of the few people allowed in before the area was sealed off after the explosion.

He said: "I saw the black smoke and didn't really think anything of it because you see a lot of that around here.

"I arrived for work early and got here to be told that the number five blast furnace had blown out.

"A lot of the boys who work here are in a terrible state."