The frenetic effort to drill into the presumed location of six workers trapped in a collapsed mine yielded no audible evidence of survivors early yesterday. But rescuers cautioned their work isn't done and that air quality in the mine could sustain life.
Using a steel drill bit to bore a 6cm wide hole more than 550m into the mountain site of Monday's cave-in, rescuers finally broke through late on Thursday, into the cavity where authorities believe the miners are trapped. A crude measurement found enough oxygen to keep the men going if they survived the collapse.
But a microphone dropped into the void failed to pick up any sounds that would indicate the miners are alive. And though the air sample indicated plenty of oxygen and no methane in the pocket, it also did not pick up carbon dioxide, the gas exhaled when people breathe.
Despite the silence, company officials remained hopeful.
"I wouldn't look at it as good or bad news. The work is not done," said Bob Murray, chairman of Murray Energy Corp, who said early yesterday that oxygen levels suggested that if the men survived the collapse, "they're going to stay alive in that atmosphere."
The air sample was sucked from the cavity through a steel tube, with a microphone attached to pick up any signs of life.
However, relatives shouldn't be discouraged by the lack of carbon dioxide, an attorney for the company said.
"What you got was a quick sample from a crude instrument, so you don't get all the constituents reported," said attorney Christopher Van Bever.
Meanwhile, drilling continued on a second, wider hole, which could accommodate a powerful camera to provide a view inside the pocket, deliver food and water, and hopefully give a more definitive answer about the miners' fate.
Work also continued in the mine itself, where rescuers were slowly burrowing through the debris to reach the workers.
"It's incredibly labor-intensive," said Rob Moore, vice president of Murray Energy.
If the miners are alive, they might be sitting in inky darkness, their headlamps likely having burned out. Wearing thin work clothes in the 14oC cold, they could be chilled to the bone if water is seeping into their chamber 150 stories below ground, other miners say. Murray said each miner would typically have had 2 liters of water.
At the time of the collapse the six miners were working in an area with a 2.5m ceiling. Corridors in the mine are typically about 4.3m wide.
The mining company has withheld the names of the six miners though the press has confirmed five identities: Carlos Payan, Don Erickson, Kerry Allred, Manuel Sanchez and Brandon Phillips.
The men's families were praying for their survival, one relative said.
"There are all types of conditions that could be in there for these folks ... some little cavity, some little corner," said Arch Allred, cousin of miner Kerry Allred.