An effort to drill a tiny hole deep into a Utah mine where six workers are trapped may have missed its mark, mine officials said Friday.
A listening device was dropped down the hole but rescue crews were unable to establish contact with any survivors. And air samples contained low levels of oxygen, suggesting crews drilled into the wrong underground chamber.
"There's no reason to lose hope. There are certain possibilities that these miners are still alive," said Richard Stickler, head of the U.S. Mine Safety and Health Administration.
Initial air samples had indicated 20.5 per cent oxygen, some carbon monoxide and no methane detected, but later samples showed less oxygen.
After days of drilling, crews finally broke through around 10 p.m. local time on Thursday.
The first air sample was drawn more than 540 metres through a steel tube, which remained in the narrow hole to keep the lifeline open in case the miners heard a tone from the microphone and tried to respond.
Drilling continues on a wider hole, which would allow rescuers to lower food, water and a camera to get a view of the pocket.
Crews also continued work in the mine itself, slowly burrowing through the debris to reach the spot where the walls caved in.
"It's incredibly labour-intensive," said Rob Moore, vice-president of Murray Energy.
Officials are hoping to reach the miners in the next five days.
If the entombed miners are still alive, they may be sitting in darkness, their headlamps having burned out. They are wearing thin work clothes in the 14C cold, 580 metres below ground.
At first, the men were believed to be buried about 455 metres below the surface in central Utah, where they became trapped after a cave-in at the Crandall Canyon mine.
The mining company has withheld the names of the six miners. The Associated Press has confirmed five identities: Carlos Payan, Don Erickson, Kerry Allred, Manuel Sanchez and Brandon Phillips.
Relatives are praying for their survival.
"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.
Meanwhile, there were more scientific findings disputing Murray's claim that an earthquake caused the collapse.
Scientists at the University of California, Berkeley, did their own analysis of Monday's seismic event and determined the seismic waves came from an underground collapse.
With files from The Associated Press
