Hundreds of rescuers struggled with falling rock and debris Monday in a desperate race to reach six coal miners trapped 1,500 feet below ground by a cave-in so powerful authorities initially thought it was an earthquake.
As the rescue stretched into the night, workers were unable to make significant progress.
"I'm very disappointed. That's one step backward," Robert E. Murray, chairman of Murray Energy Corp. of Cleveland, a part owner of the Crandall Canyon mine, told reporters at an evening briefing.
More than 16 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 dead or alive. If they survived, Murray said, they could have enough air and water to last several days.
The crew was believed to be about 4 miles from the mine entrance. Rescuers were drilling into the mine vertically from the mountaintop and horizontally from the side, Murray said.
If they are able to open an old mine shaft, Murray said, rescuers believe they can get within 100 feet of where the men are trapped.
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.
Federal mine-safety inspectors were on hand to help oversee the search.
Government mine inspectors have issued 325 citations against the mine since January 2004, according to a quick analysis of federal Mine Safety and Health Administration online records. Of those, 116 were what the government considered "significant and substantial," meaning they are likely to cause injury.
The 325 safety violations is not unusual, said J. Davitt McAteer, former head of the MHSA and now vice president of Wheeling Jesuit University in West Virginia.
"It's not perfect but it's certainly not bad," McAteer said. "It would be in the medium range."
University of Utah seismograph stations recorded seismic waves of 3.9 magnitude early Monday 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, reported to authorities around 4 a.m. But by late afternoon, they said a natural earthquake could not be ruled out and more information was needed to conclusively determine what happened.