Reporting from Washington and Montcoal, W. Va. — Emergency teams stepped up a desperate rescue effort Wednesday despite fading hopes of finding any survivors two days after a devastating explosion killed at least 25 coal miners in the Upper Big Branch mine.
Drilling crews dug three bore holes deep into the rocky mountainside, and planned two others, to vent the deadly buildup of highly combustible methane gas, carbon monoxide and coal dust that forced rescue crews to retreat early Tuesday.
Carbon monoxide pouring out of the first 1,100-foot-deep bore hole was so toxic -- nearly 300 times the concentration considered safe -- that the drilling crew was nearly overcome, officials said. A pipe was installed to divert the gas so work could resume.
The carbon monoxide levels fell sharply by evening, but officials said they would test additional air samples from inside the mine to ensure that specially trained mine rescue teams could enter safely.
"We don't know if we're going in tonight until we actually see the reading," said Kevin Stricklin, coal administrator for the U.S. Mine Safety and Health Administration.
Gov. Joe Manchin III admitted earlier in the day that rescue crews hold only "a sliver of hope for a miracle" that four missing miners had survived.
"The odds are not in our favor because of the horrendous blast we had," he told reporters who gathered at a nearby elementary school.
Officials said the explosion occurred at 3:02 p.m. Monday as 31 miners were coming off the day shift. The blast knocked out lights, communications and ventilation fans, and created a windstorm that roared up shafts to the surface, shooting rocks, dirt and debris into the air.
After the blast subsided, several miners rushed inside and found six men dead and three injured; one of the injured later died. The other two remain hospitalized after the nation's deadliest coal mining accident in more than a quarter-century.
When the gases have vented, 30 rescuers working in six teams will resume the search for the missing miners. Two teams wearing breathing apparatus will lead the way through the dark, debris-filled tunnel, and the others will provide backup and support.
"We'll ride in as far as we can, then walk in the rest of the way," Stricklin said. He said it may take several hours to make their way to the blast area, nearly five miles from the entrance.
The missing miners "may not be in the exact location we think they are, so we may have to fan out a bit," he said.
If the rescue teams cannot reach the area, he said, rescuers will dig another bore hole and lower a camera to see if any of the missing miners reached a special airtight refuge chamber that contains food, water and breathing masks. Miners carry only an hour's supply of emergency oxygen.
"We're hoping that someone had the ability to get to that chamber," Stricklin said. "There's no other way anyone could survive."
Under a 2006 federal law, coal miners are required to carry special global positioning satellite tracking devices in case of emergencies. But Stricklin said the mine operator had not yet installed transmitting and receiving equipment so the devices could be used throughout the mine.
"They did not have tracking in the section" where the explosion occurred, he said.
Ronald L. Wooten, director of West Virginia's office of miners' health safety and training, said the rescue teams had detected no evidence of survivors. "We just have hope," he said.
Initial attempts to establish contact before dawn Wednesday, by banging for 15 minutes on a bore hole pipe, failed to elicit a response.
Rescue workers also planned to detonate three small explosions on the surface to send seismic signals down to anyone alive. Miners are trained to respond to such signals by pounding on equipment or metal bolts in the mine roof.
The names of the four missing miners have not been released.
The cause of the explosion is undetermined, although the mine owner, Massey Energy Co., has come under increasing fire for a spotty record of safety operations at Upper Big Branch, including 10 citations this year for inadequate ventilation of explosive gases.
The mine was cited for two safety violations on Monday, the day of the disaster. But Stricklin said he was "very confident" that the infractions played no role in causing the explosion because they occurred several miles from the blast site.
Don Blankenship, Massey's chairman and chief executive, staunchly defended the mine's safety record, arguing that violations "are unfortunately a normal part of the mining process."
"Any suspicion that the mine was improperly operated or illegally operated or anything like that would be unfounded," he told MetroNews, a local radio network.
Several members of Congress vowed to hold hearings into the disaster and to seek tougher mine safety rules.
"Clearly we must get to the bottom of what happened, how, and who was responsible," Sen. Robert Byrd (D-W. Va.), a former coal miner, said in a statement. "And we must and will hold those parties responsible."
Tom Hamburger in the Washington bureau contributed to this report.