Murray said four rescue crews and around 200 workers had been sent to the mountainside to attempt to reach the trapped men, and were about 500 metres from the accident site late on Monday.
 
Prior earthquake
 
The miners were declared missing following the tunnel collapse at around 3:50am (0850 GMT) on Monday. The collapse is though to have occurred about an hour after an earthquake, registering 4.0 on the Richter scale, occurred approximately 30km away.
 
Seismologists in Utah said the tunnel collapse may have been misread as an earthquake, according to local media reports.
 
Murray said an earthquake struck the region before the cave-in, while the US Geological Survey reported on its website that an earthquake had occurred in the region.
 
Lamar Guymon, Emery County sheriff, said that the missing men could have been up to 900 metres underground at time of the accident.
 
Different versions
 
Guymon was quoted as saying on local radio: "I've heard several different versions about how far they are, but I know it's at least 2,000 (600 metres) to 3,000 feet. They should all be together."
 
The rescue teams sought to dig through a disused mine adjacent to the site of the accident, putting them within 17 metres of the trapped miners, but abandoned the plan late on Monday.
 
"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."