The small hole drilled into a Utah coal mine in an attempt to find six men trapped since Monday may have drifted from the target area, a federal mining official announced this afternoon.
Late Thursday night, rescuers successfully punched into a cavity where they believed the men were working during Monday's cave-in. Early this morning, mine officials snaked a microphone down the 1,800-foot-deep, 2½-inch hole into the Crandall Canyon mine; as of noon, they had heard nothing and were unsure whether the drill hole was in the right place.
The drill may have punctured a different, sealed chamber, Richard Stickler, the head of the federal Mine Safety and Health Administration, said at a noon news conference.
The microphone was attached to a steel tube, which was used to take air samples that provided mixed messages for mine officials and anxious relatives.
Initial samples showed no unnatural levels of deadly methane gas and 20 percent oxygen, which would be enough oxygen to breathe — assuming the miners survived the initial cave-in and are in the cavity being searched. The sensors failed, however, to detect levels of carbon dioxide consistent with people breathing.
Later samples showed an oxygen level at 7 percent — consistent with measurements inside a sealed chamber neighboring the target area.
"Normal oxygen is 21 percent," Stickler said, referring to the initial samples. "Once you get down to 15 percent, you start having effects. Once you get down to 7.1 [percent], it would not support life for very long."
Stickler, who urged optimism despite the conflicting air samples, said that engineers now would lower survey instruments to map coordinates and determine precisely where the drill hole ended up. It could have fallen off line, he said, as it sliced through different layers of earth.
"The advantage of the 2½-inch hole is that it's fast," Stickler said. "The disadvantage is that it's not as accurate."
Federal mine officials said this morning that they would hold off on lowering a camera into the cavity because the small hole might collapse if they remove the drilling pipe used to snake the microphone into the cavity.
Rescuers instead will wait to drop the camera into a second, larger hole — about 9 inches wide — that miners are continuing to drill. The second hole is 1,200 feet deep, 600 feet from the cavity. Workers hope to punch through to the cavity by nightfall, according to Stickler.
The wider hole would allow rescuers to deliver food and supplies to miners if they are found alive. It could also accommodate a much more powerful camera to fully scope the site.
Miners continue to clear debris from the mine tunnel to try to get to the miners, but that effort is not expected to reach the cavity for several days.
The Murray Energy Corp. has not released the identities of the six missing miners, but ABC News has confirmed five of the six names. The missing miners include Carlos Payan, Don Erickson, Kerry Allread, Manuel Sanchez and Brandon Phillips.
Erickson's mother, Lucile, told ABC News earlier this week that Don, 50, was the boss of the crew and had picked up the shift for another miner the day of the collapse.
"I'm just praying, hoping that they make contact," Erickson said.
Information from The Associated Press was used in this report.