WASHINGTON — The government should never have approved plans for the Crandall Canyon Mine in Utah, experts told a Senate subcommittee Wednesday.

The head of the Mine Safety and Health Administration responded that he would not draw any conclusions until after a full investigation.

The hearing before the Senate Appropriations Subcommittee on Labor, Health and Human Services, and Education marked the first of what is expected to be several congressional hearings into the Aug. 6 Crandall Canyon accident, in which six miners were trapped and are presumed dead, and three rescuers died trying to reach them.

Subcommittee members, as well as Utah's U.S. Sens. Orrin Hatch and Bob Bennett, asked MSHA head Richard Stickler for details on what happened in the mine, what can be done in the future to avoid other accidents and how MSHA should handle accidents in the future.

Noticeably absent from the hearing was the mine's co-owner, Murray Energy chief Robert Murray, who had been asked by the subcommittee to attend and be a witness. But Murray was "still deeply involved in the aftermath of the rescue efforts," according to the company, and could not come to Washington, D.C.

Subcommittee Chairman Tom Harkin, D-Iowa, said the senators would give Murray another chance to appear before them, but he and the subcommittee's top Republican, Sen. Arlen Specter of Pennsylvania, have not ruled out issuing a subpoena if necessary.

"We will not allow him to avoid answering questions from this subcommittee," said Specter, who called Murray "a real troublemaker on the scene," because he gave incorrect information to the media and the public.

During the hearing, Harkin and other subcommittee members asked Stickler about the "bumps," or mine structure failures, that caused the collapse Aug. 6 that trapped the six miners.

Stickler said he had never seen a mine bump as "catastrophic" as this one, which registered 3.9 on the Richter scale. The force of the bump "was so intense" that it blew out ventilation controls about a half mile from where the miners were working. Another bump killed the three rescuers trying to clear out the collapsed coal by hand.

Stickler said MSHA had approved a roof-control plan on June 15 for retreat mining in the same area where the accident occurred. He said Agapito Associates, a mining engineering company, concluded that retreat mining could be done safely and that MSHA required additional roof supports.

The same company did an earlier evaluation on retreat mining in another area of the mine and came to a similar conclusion. However, a "bump" took place there in March and MSHA did not know about it until after the August accident, he said.