WASHINGTON — Bob Murray, CEO of Murray Energy, will not appear before a Senate Appropriations subcommittee on Tuesday as originally planned.

The Senate Appropriations Labor, Health and Human Services and Education Subcommittee issued a subpoena to Murray on Nov. 16 for him to testify about the August accident at the Crandall Canyon Mine that killed nine people.

But Rob Murray, vice president of business development and external affairs, said the subcommittee has postponed the hearing. Rob Murray, Bob Murray's son, said the rescheduling had nothing to do with any conflict on Bob Murray's end.

According to the office of Sen. Arlen Specter, R-Pa., the subcommittee's top Republican, no new date has been set, but some Senate sources said Dec. 14 could be the new date. The staff of Subcommittee Chairman Tom Harkin, D-Iowa, was on a staff retreat and could not be reached.

Federal investigations are still under way to try to determine what caused the collapse in Huntington, Emery County, in August that trapped six miners underground and a second collapse days later that killed three rescuers trying to get them out.