Stephen Galsworthy, Andrew Hutin, and Len Radford died in the blast

Molten metal and super-heated gases showered over workers at Corus in Port Talbot in 2001.

Stephen Galsworthy, 25, and Andrew Hutin, 20, from Port Talbot, and Len Radford, 53, from Maesteg, all died.

A dozen other workers suffered serious burns in the explosion. The inquest is expected to last six weeks.

Dr David Osborne, coroner for Neath and Port Talbot, told jury members they would be hearing from an expert who would explain how a blast furnace worked.

The jury heard that urgent repairs on the furnace had begun the day before the explosion. Initially, all seemed fine, the coroner explained, but a problem emerged the following day.

"It soon became apparent that water was getting into the furnace and this, of course, was a problem," he said.

A number of workers took part in a meeting to discuss what to do about the problem.

"It was decided that efforts to recover the situation should continue," Dr Osborne said.

"The explosion happened about one hour and 15 minutes after that meeting."

He explained that the explosion at the furnace caused a gap through which extremely hot gases and molten metal were ejected.

On Tuesday, the jury will hear evidence from workers on duty at the time of the blast, and from those who attended the meeting.