By Laura Zuckerman
SALMON, Idaho (Reuters) - Rescuers on Monday brought in a second remote-controlled digging machine and sought to drill an air hole as they raced to free a miner trapped since Friday by a cave-in at an Idaho silver mine.
Rescuers have yet to make contact with Larry Marek, 53, a 30-year veteran of the industry.
Marek and his brother were working a vein of silver more than a mile below ground in a mine owned by Hecla Mining Company in northern Idaho when a section of tunnel collapsed for unknown reasons, according to the company.
Marek's brother escaped without injury. Marek's condition is unknown.
Rescuers aided by a remote-controlled digging machine flown in on Sunday have cleared more than 39 feet of rock and other debris from a cave-in estimated at 75 feet.
Crews are working around the clock in two 12-hour shifts.
A second drone digging machine arrived Monday and is being readied for operation. Crews also are preparing to drill a 2-inch hole in the blockage for air and to test for open areas where Marek might have found refuge.
"It's a long and serious process; we're doing everything we can to expedite the rescue effort," Melanie Hennessey, Hecla vice president of investor relations, told Reuters in a telephone interview on Sunday.
The cave-in caused Hecla to suspend commercial operations at the Lucky Friday Mine in Mullan, an 800-population town in Idaho's Silver Valley, an historic mining district along the Coeur d'Alene River near the Idaho-Montana border.
Mullan Mayor Mike Dunnigan said that generations have depended on the area's mines, which produce silver, lead and zinc.
"It's a very close-knit community; there are concerns through the whole valley about the gentleman underground," he said in a telephone interview.
Hecla officials said it will investigate the cause of the accident when the rescue effort ends.
Hecla is seeking to expand the depth of the Lucky Friday to 8,000 feet. The accident happened the same day the U.S. Department of Labor released a report faulting federal mining inspectors who oversee safety for failing in some instances last year to "properly evaluate the gravity and negligence in certain citations."
The Lucky Friday has been in production for nearly 70 years, yielding 3.4 million ounces of silver in 2010. It is one of three active mines in the United States owned by Hecla, which is based in Coeur d'Alene.
(Editing by Greg McCune)