LOS ANGELES (AFP) - Hundreds of rescuers dug through tonnes of rubble on a remote Utah mountainside on Monday to reach six miners trapped after a tunnel collapsed following an earthquake, officials said.
Authorities said they had pinpointed the location of the six miners who were digging underground at the Genwal Mine in Huntington Canyon, around 120 miles (193 kilometers) southeast of Salt Lake City at the time of the cave-in.
But Robert Murray, a director of Utah American Energy which is spearheading the rescue effort, told a news briefing there had been no contact with the miners and acknowledged they may have died.
"We know where they are. They could be trapped ... they could be dead," Murray said. "There's no way of knowing right now."
The miners were declared missing early Monday following the tunnel collapse at around 3:50 am local time (0850 GMT), around one hour after a 4.0 magnitude earthquake struck less than 20 miles (32 kilometers) away.
It was not immediately clear if the earthquake caused the accident. Local media reports quoted seismologists in Utah as saying the tunnel collapse may have been misread as an earthquake.
However Murray was adamant an earthquake struck the region before the cave-in. The US Geological Survey continued to report on its website that an earthquake had struck the region early Monday.
Emery County Sheriff Lamar Guymon told local radio the missing men could have been up to 3,000 feet (900 meters) underground when the cave-in occurred.
"I've heard several different versions about how far they are, but I know it's at least 2,000 (600 meters) to 3,000 feet. They should all be together," Guymon said.
Murray said four rescue crews and around 200 workers had been deployed in an effort to try and reach the men. Rescue workers were around 1,700 feet away from the where the men were believed to be late Monday, Murray said.
However a plan to dig through an abandoned mine adjacent to the site of the accident was stymied late Monday because of debris that was impossible to dig through, Murray said.
Rescuers had hoped to break through a sealed entrance in the disused mine shaft that would have put them within 55 feet of the miners, raising hopes of a speedy excavation to reach them.
"I'm disappointed to report that our efforts have not been fruitful in this approach," Murray said.
"Our crews are now on their way back out of the mine as they ran into impassable conditions ... they were actually driven out. But everyone got out safely."
The rescue effort revived memories of the doomed effort to reach 13 miners who were trapped after an explosion at the Sago Mine in West Virginia in January last year.
Twelve miners died while only one survived after being buried underground for 41 hours.