But crews using bore holes and probes found only sand and rubble where they had been searching for an open section of mine, said spokeswoman Melanie Hennessey.
Finding collapsed material here could mean the entire 75 feet of tunnel where 53-year-old Larry Marek had been working has collapsed.
"We would hope not, but that's the indication," Hennessey said.
There still could be open areas elsewhere inside the mine, she said. Crews won't know whether to expect to find voids without more digging. And since there is no way to know for certain Marek's location, search efforts will continue.
"We're still 100 percent focused on rescue efforts," Hennessey said.
Marek and his brother, Mike, had just finished watering down blasted-out rock and ore in an area called Stope 15, which has been mined for 14 years, Hecla said. The ceiling collapsed about 75 feet from the rock face of the 6,150-foot deep tunnel, the company said. Mike Marek, who was working at the opposite end of the collapse from his brother, escaped unharmed. The brothers might have been working more than a mile deep in the Lucky Friday Mine when the tunnel collapsed April 15.
Rescuers digging through debris in the collapsed tunnel advanced about 35 feet earlier in the week before being forced to stop by dangerous conditions, leaving about 40 feet remaining to the end of the tunnel.
Five probes have been drilled from various locations into that 40-foot section, with four finding sand and rubble and a fifth finding a void, though its size and exact location hasn't been determined, Hennessey said. She said a sixth drill probe was in progress late Saturday.
The company is also using the drill holes to put fresh air and water into the collapsed tunnel.
Hennessey said the 220-foot rescue tunnel, called a drift, had advanced to 184 feet Saturday and has about 36 feet left to reach the end of the collapsed tunnel, and that the probes are helping miners determine how to proceed.
"At this point the focus is really making sure we get an understanding of the ground conditions, to prepare for the rescue crews to enter that area through the 220 drift," she said.
She said there is no estimate on when crews will reach the collapsed tunnel. Work on the 220 drift has slowed as crews encounter increasingly difficult conditions that require a special tunneling technique called spiling that uses steel supports to prevent the new tunnel from collapsing.
She said the company has all the supplies and equipment at the mine to continue moving forward with the rescue tunnel.
No cause has been established for the cave-in. The mine has shut down production to concentrate on the rescue effort.
The Marek family has not spoken with reporters since the cave-in.
Hecla is the largest silver producer in the nation, from the Lucky Friday and the Greens Creek mine in Alaska.
