Updated 2:08 p.m. ET
BOISE, Idaho - Rescuers trying to reach a trapped Idaho silver miner on Tuesday were forced by unstable conditions to alter their operation and are now attempting to reach him from a new direction.
The changes were necessary due to dangerous conditions more than a mile underground inside the Lucky Friday Mine, said Federal Mine Safety and Health Administration Amy Louviere.
There, a collapse last Friday trapped Larry "Pete" Marek, a 53-year-old employee of Hecla Mining Co.
He hasn't been heard from since the collapse.
It's unclear just how this change of plans will impact the duration of the rescue or the time needed to reach the area where Marek might be. Company officials said the conditions underground are unstable, as rescue workers encountered a debris field laden with boulders, twisted wires, mesh and broken concrete that had been used to shore up the tunnel before it caved in.
"It changes every shift," said Stephany Bales, a Hecla spokeswoman. "It's a long tedious, process. What they're dealing with, under there, boulders, cement and wires, it isn't an easy task, by any stretch. It is unstable."
The rescue hasn't been suspended, only adapted to fit the conditions underground, she said.
In addition to the main rescue operation, there's a separate effort using a diamond drill to bore a 2-inch hole from another tunnel inside the mine. Officials at the Lucky Friday Mine, tucked into the forested mountains of the Idaho Panhandle's Silver Valley, hope to find an open area that could have provided Marek refuge behind the cave-in.
But it might take as long as two days for that drill to get through about 185 feet of solid earth, said Melanie Hennessey, a spokeswoman for Hecla, where Marek has worked for 12 years.
Before Tuesday's change in plans, workers used a remote-controlled digging machine called a mucker to advance a total of 39 feet into the collapsed area, which could be as long as 75 feet.
The process of shoring up the caved-in tunnel behind the excavation, to make it safe for rescuers to advance, had been consuming valuable time, with supports placed in only about four more feet of tunnel over a span of about 12 hours. Rescuers on Monday more than doubled their estimate on the volume of the collapse: from 10 feet high to 25 feet high.
"The amount of work needed to do the four feet, given the increase in height, is tremendous," Hennessey said.
It's unclear if Marek had communication equipment with him at the time of the accident. It could have been left in a vehicle he was using at the time.
Marek and his brother, another mine worker, had just finished watering down blasted-out rock and ore on existing mining areas when the collapse occurred about 75 feet from the end of the 6,150-foot deep tunnel, according to the company. His brother was able to escape.
The family has not commented.
All mining activity has been halted for the rescue effort, Hecla said. Officials said they will focus on how the collapse occurred once the rescue is complete.
The mine in Mullan employs roughly 275 workers, about 50 of whom were underground in various parts of the mine when the collapse occurred, Hennessey said.
On its website, Hecla describes itself as the oldest U.S.-based precious metals mining company in North America and the largest silver producer in the U.S. The Coeur d'Alene company currently produces silver from two mines, Greens Creek and Lucky Friday, which has been operational since 1942.
Silver prices have soared about 38 percent this year, and Hecla is spending $200 million to increase its production of the metal by about 60 percent. The upgrades will extend the life of the Lucky Friday mine beyond 2030.
Hecla appears to have a good record of health and safety at Lucky Friday.
The mine has reported no fatalities dating back to 2000, according to a Mine Safety and Health Administration database. The federal regulator has cited the mine for violations but none in the last year specifically tied to the kind of accident that occurred Friday.
Like mining areas around the world, northern Idaho is not immune to accidents, some of them tragic. Last June, a miner was killed in the Galena Mine in nearby Silverton after a rock slab fell on him.
In 1972, 91 miners were killed in a fire about 3,700 feet underground inside the Sunshine Mine between Kellogg and Wallace.