The Health and Safety Authority has started an investigation into Wednesday's fire in a truck in a mine shaft at Tara Mines near Navan, Co Meath.
Seventy men working underground had to gather in refuge stations before being brought to the surface. However, the company stressed that none of the men was in danger at any stage.
The fire broke out in one of the huge vehicles used to haul ore to the surface. The cause of the fire in the 50-tonne truck was still under investigation yesterday by technical and safety personnel at the mine.
Tara is the largest lead-zinc mine in Europe. It is owned by the Finnish concern, Outokumpu Oy.
About 100 miners, fitters and other employees working underground on Wednesday afternoon received an alert that fire had broken out a couple of hours before their eight-hour shift was scheduled to end at 4 p.m.
Nearly 30 workers were able to get out of the mine at once, while the others went to the refuge stations which have fresh air, water and phones.
Our Lady's Hospital, Navan, less than 10 minutes' drive from the mine, went on standby in case of injuries as soon as the fire alert was received, but no one needed to report to a doctor. Meath SIPTU branch secretary Mr Christy McQuillan, who represents the majority of Tara Mines workers, welcomed the confirmation provided by the emergency that adequate safety procedures were in place to prevent a disaster. "It's a big boost for men going 1,000 feet underground every day," he said. Tara Mines' human resources manager, Mr Colm Conachy, said he could not accurately estimate the extent of production lost due to the fire.
Falling zinc prices have forced the mine to introduce an extensive cost-cutting and productivity expansion programme, which was finalised early last year. Redundancies left the workforce at about 700. The company's daily output averages 11,000 tonnes.
Five of the huge haulage trucks are used in the network of underground tunnels at the mine.
"When we lose a major piece of equipment like that, it would have an impact, but it is difficult to quantify it yet," Mr Conachy said.
Production restarted at midnight on Wednesday.