The three men were trapped in an ore drive or stope (a horizontal mine shaft) when an earthquake measuring 2.2 on the Richter scale caused a rockfall near where they were working.

No one knows if they survived the fall because they have not made contact with anyone above ground.

The area where they were working does not have a refuge chamber - effectively a secure, ventilated emergency room available to mine employees in case of accidents.

Three workers survived a recent incident at a West Coast mine by accessing such a chamber.

Beaconsfield mine management believes that the ventilation system in the area where they are trapped is still working.

But as the hours pass, their chances of survival decrease rapidly.

"We have grave concerns for their wellbeing," mine manager Matthew Gill said yesterday.

Former mine employee Kerry Butler said: "First of all they would have had to survive the rockfalls.

"Secondly the dust would have been a problem, and after that it's a matter of getting fresh air.

"My gut feeling is not good - there are a lot of butterflies (in my stomach)."

Another 14 miners underground at the time of the tremor managed to make it to a refuge chamber in the decline area and returned to the surface via the shaft a short time later.

None of them were injured.

Mine management said the crews were not blasting at the time of the quake, but Mr Gill said the mine did blast regularly on a 24-hour basis.

Mine safety crews spent hours yesterday morning assessing the safety of the mine, before a rescue operation could begin.