Kiev - Three Ukrainian coal miners were found alive days after a tunnel collapse trapped them underground, union officials said Thursday. A roof collapse on Monday, 58 metres below ground in the Novodzerzhinsky mine in Ukraine's eastern Donetsk region. left nine miners isolated and without contact to the surface.

Rescue crews working around the clock uncovered the two dead miners shortly after 5 am on Thursday, said Viktor Tumanov, a mining union leader.

The three survivors were found sheltering in a still-standing section of the tunnel some two hours later, he said.

"They (the survivors) had been underground for more almost three days," Tumanov said. "They have been hospitalised but their condition is satisfactory and we expect them to recover."

Crews were continuing to remove rubble from the collapsed section of the tunnel and a search for three more miners thought to have been caught in the collapse was continuing.

"We are not giving up hope, they could still be alive," Tumanov said.

Rescue teams on Wednesday initially uncovered the body of one miner killed in the cave-in.

Mine officials believe a total nine miners were caught in the collapse, with three known to have died as of Thursday morning.

Officials from Ukraine's Ministry of Coal Industry were investigating the cause of the accident.

Ukraine's coal mines are among the world's most dangerous, with an average 300 workers dying on the job annually.

The most common causes of miner deaths are methane gas explosions, tunnel collapses, and equipment accidents.

Safety standards are poorly enforced in Ukrainian coal mines, and safety equipment often is outdated or absent. High unemployment prevents most coal miners from seeking less dangerous employment.

Coal as a key element of steel and energy production is critical to Ukraine's economy.