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Defense Secretary Leon Panetta said Thursday that harsh criticism of the Air Force's investigation of lost body parts at its Dover military mortuary has prompted him to order the Air Force to consider imposing stronger punishment on those responsible.

"None of us will be satisfied until we have proven to the families of our fallen heroes that we have taken every step possible to protect the honor and dignity that their loved ones richly deserve," Panetta told a Pentagon news conference.

In revealing Tuesday that it had found "gross mismanagement" at the Dover, Del., facility, where small body parts of U.S. troops killed in Afghanistan were lost on two occasions, the Air Force said it took disciplinary action -- but did not fire -- three senior supervisors there.

Gen. Norton Schwartz, the Air Force chief of staff, told a congressional committee Thursday that Col. Robert Edmondson, who commanded the Dover mortuary at the time of the incidents in 2009, had been given a letter of reprimand. He also was denied a job commanding a unit at Shaw Air Force Base, S.C., and will not get any future commands.

"This is not a trivial sanction," Schwartz said.

Two civilian supervisors at Dover -- Trevor Dean and Quinton Keel -- took a cut in pay and were moved to non-supervisory jobs at Dover. They still work there.

All three men have declined through Air Force officials to comment publicly on the matter.

Panetta said he told Air Force Secretary Michael Donley to examine whether those disciplinary actions were "appropriate," and to report back.

Just two days earlier, Panetta had commended the Air Force for the thoroughness of its investigation and said he supported the discipline imposed. Asked what prompted him to take a more skeptical view and order Donley to reconsider stiffer punishments, Panetta pointed to a report by the Office of Special Counsel that harshly criticized the Air Force for failing to accept full responsibility.

The Special Counsel, an independent federal investigatory agency, said it was unreasonable for the Air Force to assert that the mistakes made at Dover did not violate any law, rule or regulation. And it said the disciplinary actions were insufficient.

Donley issued a brief written statement after Panetta's news conference promising an "exceedingly thorough and rigorous" review of the disciplinary actions.

"The lapses in our standards at Dover, which we sincerely regret, are our responsibility to fix," Donley said.

Panetta said "all Americans, including myself, were justifiable disturbed" by the Air Force's report of serious lapses at the Dover mortuary, where all troops who die on foreign battlefields are brought for identification and processing before burial. He said Donley and Schwartz briefed him on the status of the investigation shortly after he became defense secretary in July.

"Full accountability is what we intend to deliver," he said.

Earlier this week Panetta announced an independent review of how procedures have been improved at the mortuary. He put a former surgeon general, Richard Carmona, in charge of that 60-day review.

Panetta also said the families of those whose remains were mishandled deserve an apology. He indicated he was not aware that those families were not told about the mistakes and the Air Force's investigation until last weekend -- months after it was finished.

"The families should have been alerted earlier," he said.

In its investigation, which began in May 2010 and was completed in March 2011, the Air Force confirmed allegations by three Dover whistle-blowers that pieces of body parts from the remains of U.S. troops killed in Afghanistan were lost on two occasions -- in April 2009 and July 2009.

It also said that in January 2010 a protruding arm bone of a dead Marine was sawed off in order to fit his remains into his uniform for viewing by his family. The family was not asked for permission to remove the bone and was not informed afterward.

"There clearly were unacceptable mistakes made," Schwartz told the Senate Armed Services Committee. "Whether they constitute wrongdoing is another matter entirely."

Sen. Claire McCaskill, D-Mo., said she has called on Schwartz and Donley to investigate the Air Force inspector general, whose office investigated the matters at Dover. She said there are questions about whether the inspector general, Lt. Gen. Marc E. Rogers, acted "with an unbiased focus on the facts."

After the hearing, Schwartz was asked by reporters about the scandal's impact on Air Force leaders' credibility.

"When we don't perform to standard, clearly it affects people's perception of their Air Force," he said. "We know that. And we take responsibility for that."