The smaller of the two boreholes drilled last week reached its destination Friday, but no response was heard at the surface from the six trapped below. A larger borehole measuring about 8 to 9 inches also did not provide positive news for family members and the mine’s owners, Murray Energy and Intermountain Power.

The drill for the third borehole was scheduled to be set Sunday evening Utah time. According to estimates, it will be dropped more than 1400ft.

Murray Energy founder Robert Murray said Sunday that the third target will be in an area where officials anticipate the group would have gone to in the event of bad air in their initial location. Neither he nor anyone else involved provided an estimate as to when the hole would reach the underground space.

The Mine Safety and Health Administration’s Richard Stickler told the public in a news conference that poor lighting allowed the camera dropped from the second hole to see only about 15ft, much less than its 100ft capability.

“Our attitude is we always have to have hope, and our position is that we're hoping and we're praying and it would be a terrible mistake to give up hope until you know for sure," he said, adding that another attempt will be made with better lighting.

In the meantime, crews are forcing compressed air into the space to get into the mine.

Underground rescue attempts were also slowed by a series of additional bumps, various reports have said.

The route was blocked 2000ft from the men, said national news service CNN, and as of Saturday evening Utah time debris had been cleared from that route about 650ft. Officials said the pace had also been slowed due to the need to install extensive roof and wall supports with each advance.

Meanwhile, experts are calling the damage to the mine Monday the result of heaving, not a roof collapse. According to Stickler, debris looks to have rolled in from the ribs rather than from the roof.

“The roof line has not collapsed and even in the area where we're doing the clean-up work, we do not see any collapse … of the roof itself," he said Saturday.

Other sources noted to the Associated Press that pressure appears to have pushed the floor upwards.

“It was a heave,” said a family member of one of the six trapped miners, and another told the news service that the floor lifted approximately 2ft.

Professor Jerry Tien from the University of Missouri-Rolla explained to the AP that if pillar removal did cause the heave, the blame would not necessarily be any pillar removal – but rather an incorrect estimation of floor strength.

“We're dealing with a lot of unknowns when we go underground,” Tien said.

“We try to know as much about the floor as possible but we can never know everything.”

Keep watching International Longwall News for further updates on this story.