HUNTINGTON, Utah (AP) Rescue crews clinging to a mountainside struggled Wednesday to drill two narrow holes one just 2 1/2 inches across, the other less than 9 inches in a painfully slow effort to bring air and food to six miners trapped in a cave-in.Officials held out hope that the men survived Mondays thunderous collapse and that the emergency supplies would help keep them alive while other rescuers tried to punch their way through the rubble in the mine shaft and bring them out.The crews drilling the two parallel relief holes made encouraging progress Wednesday and could break through by Friday, said Bob Murray, chairman of mine co-owner Murray Energy Corp.I consider this to be very, very good news, he said. But it could take at least seven days to actually reach the men and bring them out, Murray said.The drilling of the relief holes involved boring an extraordinary 1,500 feet straight down, or 150 stories into the earth, through hard sandstone a task that required precise alignment of the drill and posed the constant risk of a broken bit.Nothing has been heard from the men since the cave-in, not even the hammering on the ceiling that miners are trained to do in an emergency.The parallel effort to clear a path inside the blocked mine suffered a major setback Tuesday when seismic shocks wiped out all progress in removing rubble.Murray offered no estimate on how long the miners could survive that is, if they are still alive but backed off a claim Tuesday that they could subsist for perhaps weeks on available air.The oxygen depends on the size of the cavity they are in, and I have no idea what size that cavity is, he said Wednesday.The task illustrated the specific 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 into the earth.Over the past few days, the rescuers had to bulldoze 8,000 feet of road across the wilderness and use a helicopter to bring in heavy equipment. They had to balance their drilling rig on a 23-degree mountainside. And then they had to begin boring 1,500 feet straight down into the earth.The circumstances made the rescue operation extremely hard, one of the toughest weve had to deal with, said Allyn Davis, who oversees Western mine safety operations for the federal Mine Safety and Health Administration.The smaller relief hole was 450 feet deep by early Wednesday, Murray said.In two days, if they continue this pace, that hole will be down to where we want it to be, Murray said, adding that if the men are still alive we can provide everything they need, including a toothbrush and a comb, to keep them alive until the underground effort gets to them.Drilling began Wednesday morning on the larger relief hole, and there was no immediate report on how far the work had gotten.The Crandall Canyon mine is built into steep sandstone cliffs in the Manti-La Sal National Forest, 140 miles south of Salt Lake City.The drillers had to be careful to keep the massive drill rig properly aligned while balancing it on the steep side of the mountain.If you dont have it aligned properly, youre going to miss your target, said Richard Stickler, head of the federal Mine Safety and Health Administration.The height of the mountain and the extreme depth of the mine combined to require a lot of drilling.Said Davis: I just hope and pray we dont run into problems with broken bits or a broken drill stem.By contrast, the Quecreek mine in Somerset, Pa., where nine miners became trapped in a flood in 2002, was just 240 feet below ground, and it took rescuers 77 hours to reach the men. The Sago mine in West Virginia where 12 were killed in an explosion last year was 260 feet down.Drilling through that hard sandstone is going to take a while. In West Virginia, Pennsylvania, its easier to get to and you dont have to drill as far. Back there drilling a 300-foot hole is a few hours worth of work, said Bob Ferriter, mine safety and health program manager at the Colorado School of Mines. Here, getting that drilling rig to top of a mesa through that hard sandstone, thats a more monumental task.Murray spoke to reporters Wednesday after meeting with the miners families at a school in Huntington, 10 miles away. At one point, he left the building, paced outside and returned.Maria Buenrostro, the sister of trapped miner Manuel Sanchez, 41, 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, thats all we want, said Buenrostro, 40. If theres nothing that they can do about it, you know, just tell us so we know what to expect when they bring them out.Murray said the families had thanked him.You cant make everybody happy, he said. In a trauma like this, as the days wear on, tensions become more and more. I have been truthful with them.Associated Press writers Jennifer Dobner in Huntington, Utah, Brock Vergakis in Salt Lake City and Vicki Smith in Morgantown, W.Va., contributed to this report.