Ted Robbins, NPR
A miner walks away from the entrance to Crandall Canyon Mine this week during rescue efforts.
Electronic receivers have picked up some faint sounds from Crandall Canyon Mine in Utah, where six workers remain trapped 10 days after the mine's collapse. Video images have also detected an undamaged area where the miners may have been able to retreat.
In an interview with James Hattori, the co-owner of Murray Energy, which owns the mine, says it is not certain whether the sounds represent human activity.
"We are hopeful enough that it might have been one of the trapped miners signalling us that we are now drilling at that location where we think the sounds emanated from," Bob Murray says.
Murray says that rescue efforts underground have been hampered by seismic activity. Regarding the question of whether the collapse was caused by an earthquake or by faults in the mine, Murray says, "You can't simplify it that way. The original forces that caused this, that I said caused it, the report and investigations already show that I was correct.
"[The cause] we can deal with later. I am focused right now on getting these trapped miners out alive and dealing with their families."