Work continues on the larger borehole, estimated at 9in, but the other – reportedly measuring 2.5in – had drilled into the earth about 1530ft by 11am Utah time and the company said drillers were within 70 feet of the cavity they hoped would contain the miners as of about 4.30pm local time.

“We should arrive in the cavity in six hours," Murray Energy chief Robert Murray said in a noontime press conference during the fourth day of rescue efforts.

“They know we're on the way … those men probably can hear that drill rig right now, if they're alive.

However, he cautioned, “We may get no noise. They may be dead.”

He added that audio and visual equipment was onsite at the mine for use when the hole is complete, but reminded the public that the drilling may have missed the mark because global positioning, or GPS, was used to determine where to bore. If that’s the case, “we would have to start drilling again,” he said.

The larger of the two boreholes had progressed only about 355ft by midday Thursday and is expected to reach the area of the workers sometime Friday evening. Its commencement was delayed, officials have noted, because 8000ft of road had to be constructed in order to get the unit to the needed location; it also had to be perched at a 23-degree angle due to the topography of the area.

In the meantime, underground crews continue to dig through debris at a rate of about 300ft per day to reach the six that are believed to be about 3500ft from the portal entrance and under about 1500ft of overburden. It could be a week or more, officials have said, before rescue teams reach them that way.

Murray expressed his concern for everyone involved in the rescue mission, saying their safety was key as they continue their work towards the group.

“Some of these men are willing to take chances to get their brothers out. We can't allow that,” he said.

Identities have now been reported by various outlets for the six miners: Manuel Sanchez, Kerry Allred, Don Erickson, Brandon Phillips, Carlos Payan and Luis Hernandez. Their positions held at the operation are not yet known, and only Sanchez’s age, 42, has been disclosed.

MSHA remaining involved

Throughout the effort to rescue the miners that began shortly after the cave-in during the early morning hours of Monday, August 6, the US Mine Safety and Health Administration has provided support in the form of individuals onsite at the Huntington, Utah mine – about 150 miles south of Salt Lake City – and through regular public updates.

“Currently, 39 miners are underground conducting rescue work,” the agency said in a midday statement Thursday.

“The continuous miner began excavating at crosscut No. 120, No. 1 entry and advanced to the No. 121 crosscut.

“The miner has been backed out so that roof bolts can be installed at this crosscut.”

MSHA also provided a series of questions and answers, many relating to the operation’s violation and fine history.

Crandall Canyon, it noted in the multi-page document, confirmed an average 80 violations at the mine annually. However, it noted that level to be less than others in its sector.

“The violation incident rate for a mine of this classification [underground bituminous coal mines] is below the national average,” the agency said.

Whether or not any existing violations the mine may or may not have had that would have played a role in the collapse, MSHA said, will be left to the investigation team that will prepare a report on the incident.

“[Our] accident investigation team will review the past violations issued at the mine and establish the conditions that existed at the mine prior to the accident,” the agency said.

“The accident investigation report will determine the root cause of the accident and whether there were any contributory violations that led to the accident.”

It did note, however, that no roof falls have been reported at Crandall Canyon since 1998 and that its rates for fatal injuries and total incidents have been below average nationally for more than a decade.

Per the Mine Act, MSHA confirmed that quarterly inspections of the mine, owned by Utah American, are performed.

“The last inspection day underground was July 18, during a regular inspection. Although an inspector was at the mine on July 23, 2007, it was for an electrical technical inspection,” officials for the agency reported, adding that during the regular inspection, it issued 11 citations and one order.

The redundant hard-wired communications systems installed at Crandall Canyon, MSHA explained, were both likely damaged in the collapse, as no successful communications have yet been made with the miners.

Keep watching International Longwall News for the latest on this incident and rescue efforts.