Crews drilling toward six trapped coal miners in Utah hoped to reach the area where they were believed to be by Thursday night and finally discover whether the men were alive, one of the mine's co-owners said.
Authorities thought the men were 1,500 feet (457 meters) underground, but rescuers realized partway through the day that because of rough, uneven terrain, they would need to drill to nearly 1,900 feet (579 meters).
"It's not an operational problem. It's a time setback," said Allyn Davis, who oversees Western operations for the Mine Safety and Health Administration.
• PHOTO ESSAY: Utah Mine Collapse
The 2 1/2-inch (6.35 centimeter) hole to bring a microphone and camera into the cavity must be drilled 1,869 feet (570 meters), he said. The rig had reached 1,530 feet (466 meters), said Bob Murray, chairman of mine co-owner Murray Energy Corp.
A larger hole, just under 9 inches to bring food and water, must be drilled 1,886 feet (575 meters), Davis said. That drill had advanced 350 feet (107 meters) to 400 feet (122 meters).
"We will put cameras down. We will provide communication. We will provide food. We could keep them alive indefinitely," Murray said.
The miners were believed to be about 3 1/2 miles (5.5 kilometers) from the entrance to the Crandall Canyon mine, 140 miles (225 kilometers) south of Salt Lake City.
"With a little help from God and a little luck, they'll get out," said mine safety manager Bodee Allred.
The miners' families have been receiving private briefings on the rescue effort from Murray, who said he took two relatives of the trapped miners underground Wednesday to show them the rescue efforts.
Murray's company has 19 mines in five states, facilities that vary widely in the number of fines, citations and injuries, according to an Associated Press review of federal Mine Safety and Health Administration records.
At Crandall Canyon mine, the safety record was remarkably good, said R. Larry Grayson, a professor of mining engineering at Penn State University.
In a narrow canyon surrounded by the Manti-La Sal National Forest, two parallel shafts lead deep into the mine, linked by smaller tunnels about every 130 feet (39.6 meters). The walls of both passageways appeared to have imploded, creating a debris pile of dirt, coal and splintered timbers that nearly fills the 8-foot by 14-foot mine shafts.
Rescuers are clearing out the left tunnel, where the miners were believed to be trapped.
A crew of about 15 workers was shoring up the side walls and roof Wednesday and scooping the rubble, which is taken to a conveyor belt and removed from the mine. The process moves about a foot farther into the shaft each minute.
On the mountain above the mine, the drilling effort illustrated the dangers associated with the type of deep mining practiced in the West, where the terrain is rougher than it is in Appalachia and the coal mines are dug far, far deeper.
In recent days, the rescuers had to bulldoze 8,000 feet (2,438 meters) of road across the wilderness to bring in one rig and use a helicopter to bring in the other. One rig had to be balanced on the 23-degree mountainside.
The circumstances made the rescue operation "extremely hard, one of the toughest we've had to deal with," Davis said.
Ten miles away in the small town of Huntington, several hundred people filled bleachers at the rodeo grounds Wednesday night for a candlelight vigil.
At one point during a meeting at a school earlier Wednesday with the miners' families, Murray stepped outside, paced around and went back in.
Maria Buenrostro, the sister of trapped miner Manuel Sanchez, said Murray got angry with relatives' questions and walked out. She also said there was no interpreter for three Spanish-speaking families.
"We want the truth, that's all we want," said Buenrostro, 40. "If there's nothing that they can do about it, you know, just tell us so we know what to expect when they bring them out."