Bob Murray, founder and chairman of Cleveland-based Murray Energy Corp., listens to company vice president Rob Moore give an update on the rescue attempt at the Crandall Canyon Mine on Thursday northwest of Huntington, Utah. Six coal miners have been trapped since Monday.

Huntington, Utah ? If the six trapped miners are alive, they may be sitting in inky darkness, their headlamps having burned out. Wearing thin work clothes in the 58-degree cold, they could be chilled to the bone if water is seeping into their chamber 150 stories below ground.

How much air they might have is anyone’s guess.

On Thursday, more than three days after the thunderous cave-in, a drilling rig on the mountain above the Crandall Canyon mine closed in on the men, trying to bore a hole a mere 2 1/2 inches wide to bring them air and lower a two-way communication device and a tiny camera to check for signs of life.

“We may get no noise,” cautioned Bob Murray, part owner of the mine. “They may be dead.”

The drilling rig was erected on a mountain 1,869 feet above the presumed location of the men and had drilled to about 70 feet away by late Thursday. A bigger drill boring a nearly 9-inch-wide hole had reached 860 feet, slowed by a motor that broke and had to be replaced. The bigger hole could be used to lower more sophisticated cameras and provisions into the ground.

Richard Stickler, head of the federal Mine Safety and Health Administration, did not offer a timeline for the drills to reach their target depths, but a mining company news release predicted the smaller drill would reach its target early this morning.

When the small drill reaches the miners’ depth, it is expected to take two hours to withdraw it and lower a two-way communication device, said Rob Moore, vice president of Murray Energy Corp. A simple downward-pointing camera with limited visual range will also be lowered.

“I don’t want to estimate when we may break through on the cavity. We’re hopeful it will be very soon,” Moore said.

Murray warned earlier that things could go wrong, including equipment breakdowns and the possibility the drilled holes could be off target.

Simultaneously, rescuers struggled to clear rubble from a horizontal tunnel in an attempt to actually reach the miners and bring them out. But progress was slow at about 300 feet a day, and officials said it could take a week or more to break through to the miners.

“It’s incredibly labor-intensive,” Moore said.

The miners were working in an area with an 8-foot ceiling, and the corridors in the mine are typically about 14 feet wide, officials said.

Murray said that if the miners survived the cave-in itself, they would probably be spending most of the time in the dark to conserve their headlamp batteries, which are generally good for about 12 hours each.

Their other materials typically include a half-gallon of water each, he said.

Whether air is flowing into the chamber where they were working or is running out is not known. But officials had some reason for optimism, because there was no fire or explosion to consume oxygen or poison the air.

The Mine Safety and Health Administration said each miner also should have had at least two emergency air packs, each of which supplies about an hour’s worth of oxygen. But whether the air packs were within reach is not known.

Mine operators are also required to keep enough rations for 96 hours, so the Utah miners might have tried to retrieve those, if they were present.