HUNTINGTON, Utah - Seismic activity has "totally shut down" efforts to reach six miners trapped below ground and wiped out all the work done in the past day, a mine executive said Tuesday.

"We are back to square one underground," said Robert E. Murray, chairman of Murray Energy Corp., owner of the Crandall Canyon mine.

Still, "we should know within 48 to 72 hours the status of those trapped miners," Murray said.