HUNTINGTON, Utah (CNN) -- A panel of experts said the Crandall Canyon coal mine is so unstable that it would be "unacceptable" to resume digging through it to save six trapped miners.
Richard Stickler, director of the Mine Safety & Health Administration, delivers bleak news about miners.
Richard Stickler, head of the federal Mine Safety and Health Administration, said eight experts examined the condition of the central Utah mine and found "overwhelming" evidence that unpredictable seismic activity and unstable mine pillars make it too dangerous to continue rescue efforts.
The rescue effort was halted Thursday after three workers were killed and six injured in a cave-in.
But Stickler said if there is any indication the miners are alive, they would consider digging an opening down to them from above and try to get them out with a rescue capsule.
The device was used to haul nine miners to safety after a 2002 accident at the Quecreek Mine in southwestern Pennsylvania.
So far, crews have dug four bore holes into the mine, finding no signs of the miners and too little oxygen to sustain life. Watch why the mine owner is no longer optimistic about the rescue mission »
An emotional Bob Murray, the CEO of mine owner Murray Energy Corp., told reporters Monday night that rescuers have "not left a stone unturned" in trying to find the missing miners.
"There's still hope that we could find live trapped miners," he said. "It's still a rescue effort. We're not giving up yet."
"We will continue to do everything ... that is possible to bring this to an end as soon as possible," he said.
Families of the missing men have accused officials in charge of the rescue effort of giving up, urging Murray and federal officials to drill a hole large enough to send down a rescue capsule.
But Murray said that absent any indication the miners are alive, "the inherent danger of such an operation would risk too many lives."
However, he said the equipment that would be needed to attempt a top-down rescue was on its way to Crandall Canyon, in case signs of life are found.
Murray said he met with family members of the missing men Monday and conceded his message about the indefinite suspension of the underground rescue was not well received.
"Some are quite distraught right now, and that is very understandable," he said. "I was a messenger they didn't want to hear."
Friends and family have identified the six missing miners as Luis Hernandez, Manuel Sanchez, Kerry Allred, Carlos Payan, Brandon Phillips and Don Erickson. E-mail to a friend