"We are sparing no expense to bring in every mining machine in Utah in here," Murray said. One such rescue attempt would be to drill down into the mine or to make a horizontal approach through older mines that were closed in 2004. One avenue being explored is to use a helicopter to fly in a drilling rig, but Murray said, "I don't think that is the quickest way to get to them."

What caused the mine's collapse is still being debated. Authorities initially believed that an earthquake in the area may have triggered the collapse. Now, the University of Utah Seismograph Station said there is no evidence that a quake could have caused the collapse.

An "event" measuring 3.9 on the Richter scale struck about 16 miles from Huntington. Guyman said emergency dispatchers were notified of the event by the U and then some time later received a call about the mine collapse.

"We reported that the earthquake was in the Huntington Canyon area of the Wasatch Plateau. And it was apparent to us that the epicenter was in the vicinity of the Crandall Canyon Mine," Walter Arabasz, the director of the University of Utah Seismograph Stations, told the Deseret Morning News.

Speaking to reporters, Murray disputed that the mining could have triggered an earthquake. Murray said his understanding is the "epicenter" of the activity is 5,000 feet, or nearly a mile, from the trapped miners.

However, Arabasz said, "There is an uncertainty of plus or minus a mile horizontal error in an earthquake location."

The 3.9 magnitude shock was the only seismic event recorded by the network, he said, meaning that the monitors did not separately pick up an earthquake and then the signature of a mine collapse. "What I can say at this point is, again, the seismic recordings we observed are more consistent with a collapse type event in a mine rather than with an earthquake."

Experts will continue piecing together the details of the seismic event, he added. Within a day or two they should have more definitive information.

The men's identities have not been released, although officials said there were four Hispanic workers and two Caucasian employees of varying ages.

The mine stocks water in several areas and the workers would have taken "large lunches" with them, Murray said.

"We'll all be here until we can get them out," Murray said.

Throughout the day, mine workers came in and out of the mine entrance — some were called into help and others showed up to offer assistance. One black truck pulled out with a gold license plate cover that read, "United Mine Workers."

Federal officials were also on scene, including investigators from MSHA.