Rescuers trying to reach a trapped Idaho silver miner on Tuesday were forced by dangerous conditions to shift their efforts to a new route, more than quadrupling the distance that officials say workers must dig through to reach him.

They're also still trying to get a separate air hole to Larry "Pete" Marek, a 53-year-old employee of Hecla Mining Co., who was trapped Friday in the cave-in and hasn't been heard from since. The company expected to complete the air hole Tuesday.

Instability deep inside the Lucky Friday Mine led to the shift in plans to reach Marek, said Federal Mine Safety and Health Administration spokeswoman Amy Louviere.

Before, workers needed to clear through about 40 feet of the collapsed area; from the new, safer set-off point more than a mile underground, workers face as many as 225 feet left.

It's unclear just how the 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's a long tedious, process," said Stephany Bales, a Hecla spokeswoman. "What they're dealing with, under there, boulders, cement and wires, it isn't an easy task, by any stretch. It is unstable."

The company says its new effort will include blasting the rock with a jumbo drill, removing the material and then buttressing the newly exposed ground to keep it from collapsing, too.

"The drifting procedure is a standard mining method," Hecla said in a statement.

Louviere, whose agency has set up a command center at the Lucky Friday Mine, said the effort to use a diamond drill to bore a 2-inch hole from another tunnel inside the mine continues, with completion hoped for on Tuesday.

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. The distance to drill is 184 feet; as of early Tuesday, about 110 feet had already been penetrated. Once it's competed, they'll try to pump air inside.

Mine officials say the haphazard nature of the collapse means there are likely pockets in the debris, so somebody trapped inside could still be alive.

"There's pockets here and there," Hecla spokeswoman Melanie Hennessey said. "There's air getting through."

Before Tuesday's change in plans, workers had been using a remote-controlled digging machine called a mucker, advancing a total of 39 feet into the collapsed area, estimated at 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.

In the end, however, they could go no further without risking their own lives.

"Rescue operations have been suspended from the west side ... due to worsening ground conditions," Louviere said in a press release. "Further mucking will not be taking place in the caved area at this time."

It's unclear if Marek, a 12-year Hecla employee, had communication equipment at the time of the accident. It could have been left in a vehicle he was using at the time. He likely had water, his lunch pail and protective equipment with him.

Marek and his brother, Mike Marek, 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.

They had been working at roughly opposite ends of the stope, or active mining area, when the collapse occurred, with Larry working furthest from the exit.

The family has not commented. Federal officials said many of the family's members work at the mine.

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.