Rescue teams tunneled closer Monday to 13 coal miners who have been trapped in a flooded shaft for four days by icy water from an underground lake.

Working from an adjacent mine, the rescue teams are digging closer to where the trapped men are believed to have fled after a subterranean lake burst through a shaft and blocked their escape, the Interfax news agency reported.

"The prognosis is rather comforting and we expect the rescuers to reach the miners in the early hours of Tuesday," Alexander Kornichenko, deputy chairman of the Russian mine safety authority, told Interfax.

Authorities rescued 33 miners Saturday from the Zapadnaya (search) mine in southern Russia. Officials said they believe the trapped men fled to a dry area and are probably still alive.

Rescuers have drilled 40 yards of the approximately 53 yards they must pass through to reach the mine where the men are trapped, Interfax said.

"As long as they have oxygen and water, they have a chance to survive," Kornichenko told ITAR-Tass. "We are doing everything possible, and even impossible, to find the miners alive."

There were 71 miners working in the mine in the Rostov-on-Don (search) region, about 600 miles south of Moscow, when the accident occurred. Twenty-five men managed to escape after the leak filled several shafts.

ITAR-Tass said it was the second such accident at the Zapadnaya mine this year. It said water flooded the mine in February, but there were no people inside at the time.

Russian miners stage frequent protests over wage delays and declining safety standards in the country's coal industry. According to the Independent Coal Miners' Union, 68 miners were killed on the job last year and 98 in 2001.