(CNN) -- Rescue workers continued digging through rocky earth more than 6,000 feet underground Sunday in an attempt to locate a 53-year-old man trapped when the roof of the northeast Idaho mine he was working in collapsed.
Hecla Mining Company, which owns and operates the Lucky Friday mine outside Mullan, on Sunday identified the missing man as Larry Marek. An employee with the company the past 12 years, Marek has more than 30 years experience in the mining industry, Hecla said in a statement.
Ten-member rescue squads, rotating in and out over two 12-hour shifts, have been working round-the-clock to try to locate Marek. By midday Sunday, they had cleared 32 feet of the roughly 75 feet of earth that caved in around 5:30 p.m. on Friday, according to Hecla.
Marek was one of two men working in that part of the Lucky Friday mine when a 10-foot by 20-foot section of mostly rock fell on him, said Hecla's President and CEO Phil Baker. This all occurred roughly 6,150 feet below the earth's surface.
While the other man -- who has not been identified -- got out unharmed, Marek hasn't been heard from since.
"We're doing everything we can to reach the employee and will continue to make every effort, as long as it takes," Baker, whose company has run the mine in the Coeur d'Alene region since 1958, said Saturday. "We are going to bring him out."
Baker said the cause of the collapse has not been determined, promising an investigation "after the rescue efforts are complete." Numerous special bolts and chain-link fence are used to keep the ground above the affected mine in place.
Marek was trapped in a part of the mine where ore is removed and far from either of two possible exits, neither of which was adversely affected by the collapse, according to Baker.
Dexter, who formerly ran the Lucky Friday mine for Hecla and is now serving as a spokesman, explained that rescue workers don't have to dig down over 6,000 feet from the surface to get to the spot where the incident occurred. Rather, they and their equipment take a large elevator down 5,900 feet into the earth, then go north a mile and up a ramp toward the site.
Workers had been able to clear out one-third of the ground material that fell by Saturday afternoon. But the effort slowed considerably since, because of the challenges in securing the earth and preventing further collapses.
"The first 25 feet came fairly quickly," said Dexter, who recently retired from his job managing the Idaho mine. "Once we had reached that limit ... to where they couldn't go any further, that is where it becomes slow and we have to (stabilize) the roof" of the mine.
By Sunday, Hecla had "sufficient materials and equipment ... on-site to expedite rescue efforts, according to the company's statement. A special piece of machinery was flown in late Saturday from the East Coast to help in the operation.
One tool that will be employed is a "remote control mucker," which first will be taken apart, brought below in pieces, then reassembled underground. There, it will remove material at the site -- manipulated by crews who are relatively far away from danger -- Hecla said in its statement.
As is, workers are using wood and other tools to shore up the tunnel's roof (and prevent another collapse). They'd installed 20 feet of timber, for ground support, by midday Sunday, according to Hecla.
Lucky Friday is a "deep underground silver, lead and zinc mine" near the small town of Mullan, according to Hecla's website. It has been in operation since 1942, according to Dexter.
Hecla has 275 of its employees routinely working at the mine, in addition to about 100 contractors, according to a company statement. Its website describes the Coeur d'Alene-based company, founded in 1891, as the "largest and lowest-cost silver producer" in the United States.
CNN's Greg Botelho contributed to this report.