By Laura Zuckerman
SALMON, Idaho (Reuters) - A drone digging machine arrived on Sunday at a silver mine in Idaho where a lone worker has been trapped by a cave-in more than a mile underground with no outside contact since late Friday.
The miner, Larry Marek, 53, a 30-year veteran of the industry, was tapping a vein of silver in a mine owned by Hecla Mining Company in northern Idaho when a section of tunnel collapsed for unknown reasons, according to the company.
A second miner he was working with escaped without injury, but rescuers have had no contact with Marek since the accident on Friday evening. His condition was unknown.
Commercial operations at the Lucky Friday Mine were immediately suspended, and the mine was in "full rescue operation," company officials said.
"We are in communications with the family and have been keeping them up to date," Melanie Hennessey, a Helca executive, said in a statement on Sunday. "Our thoughts and prayers are with the family and friends."
As of Sunday morning, 10-person rescue teams working around the clock had cleared about 25 feet of an estimated 75-foot blockage in a collapsed corridor separating crews from the trapped miner, securing the ground as they advanced.
The company flew in a special excavation machine known as a mucker that can be operated by remote control. The drone digger arrived on Sunday morning and had to be disassembled to be taken a mile down into the mine and put back together.
Mine officials said the mucker would accelerate the pace of digging since the time-consuming practice of securing the tunnel roof as digging proceeded was unnecessary for a drone.
Hennessey, Helca's vice president for investor relations, said they company was focused entirely on the rescue and has not yet "focused on why and how this occurred."
The accident comes as Hecla is seeking to expand the depth of the Lucky Friday to 8,000 feet. It occurred 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."
Hecla employs 275 workers and 100 contractors at Lucky Friday, a hard-rock mine in an historic silver-mining district east of Coeur d'Alene, Idaho, near the Idaho-Montana border.
The operation uses a mining method known as cut-and-fill, where cuts into silver-bearing ore are back-filled with waste rock before a new section of the vein is tapped. The ore is hauled to the surface, where it is milled into a concentrate shipped to British Columbia for smelting.
The mine, which has been in production for nearly 70 years, yielded 3.4 million ounces of silver in 2009.
Lucky Friday is one of three active mines in the United States owned by Hecla, which is based in Coeur d'Alene.
(Editing by Steve Gorman and Peter Bohan)