HUNTINGTON, Utah - Hundreds of rescuers broke through walls of rock yesterday in a desperate race to reach six coal miners trapped 1,500 feet below ground by a cave-in so powerful that authorities initially thought it was an earthquake.

Hours after the collapse, which did not appear related to an explosion, searchers had been unable to contact the miners and could not say whether they were alive. If they survived the collapse, a mine executive said, they could have enough air and water to last several days.

"We're going to get them," said Robert E. Murray, chairman of Murray Energy Corp. of Cleveland, a part-owner of the Crandall Canyon mine. "There is nothing on my mind right now except getting those miners out."

The mining crew was believed to be about four miles from the mine entrance. Rescuers were working to free the men by drilling into the mine vertically from the mountaintop and horizontally from the side, Murray said. Officials said drilling vertically could take three days.

If they are able to open an old mine shaft, he added, rescuers believe they can get within 100 feet of where the men are trapped.

"The idea is to get a hole into where they are," Murray said. "They could be in a chamber 1,000 feet long, or they could be dead. We just don't know right now."

Doug Johnson, director of corporate services at an affiliated company, UtahAmerican Energy, said rescuers had made "decent progress" but were not much closer to the men.

Relatives of the miners waited for news at a nearby senior center.

The mine uses a method called "retreat mining," in which pillars of coal are used to hold up an area of the mine's roof. When that area is completely mined, the company pulls the pillar and grabs the useful coal, causing an intentional collapse. Experts say it is one of the most dangerous mining methods.

Federal mine-safety inspectors, who have issued 325 citations against the mine since January 2004, were on hand to help oversee the search.

Murray said no expense would be spared to save the men. The company had enlisted the help of 200 employees and four rescue crews, and brought in all available equipment from around the state.

The mine is built into a mountain in the rugged Manti-La Sal National Forest, 140 miles south of Salt Lake City, in a sparsely populated area.

By midafternoon, rescuers were within 1,700 feet of the miners' presumed location, Murray said. It was not known what kind of breathing equipment the miners had.

University of Utah seismograph stations recorded seismic waves of 3.9 magnitude early yesterday in the area of the mine, causing speculation that a minor earthquake had caused the cave-in.

Scientists later realized the collapse at the mine had caused the disturbance. But by late afternoon, they said a natural earthquake could not be ruled out and more information was needed to conclusively determine what happened.

Murray believed the miners have plenty of air because oxygen naturally leaks into the mine. The mine also is stocked with drinking water.

"They should have lots of oxygen to breathe," said Mary Ann Wright, associate director for mining in the Utah Division of Oil, Gas and Mining.

Of the 325 citations issued against the mine since 2004, according to a quick analysis of federal Mine Safety and Health Administration online records, 116 were what the government considered "significant and substantial," meaning likely to cause injury. Inspectors have issued 32 citations against the mine this year, 14 considered significant.

Asked about safety, Murray said: "I believe we run a very safe coal mine. We've had an excellent record."

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