tiny microphone lowered deep into the earth early Friday picked up no evidence that six coal miners are alive four days after they were caught in a cave-in. But an air sample indicated enough oxygen to breathe was present in the chamber where the miners are believed to be trapped, and rescuers promised to keep digging toward them.
Using a steel drill bit to bore a 2 1/2-inch wide hole more than 1,800 feet into the mountain site of Monday's cave-in, rescuers finally broke through late Thursday. Though a crude 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.
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