The men were to appear before the committee Wednesday at the open hearing looking into allegations a ringleader of the attacks was identified as a potential terrorist a year before the attacks.
The group gagged was involved with a special military unit called Able Danger, charged with terror identification and assessment.
"We have expressed our security concerns and believe it is simply not possible to discuss Able Danger in any great detail in an open public forum," Bryan Whitman, a Defense Department spokesman told The New York Times.
Two military officers who were part of the group said they tried to share the information about Mohamed Atta, the Egyptian-born ringleader of the attacks, with the FBI in the summer of 2000, but were blocked by Defense Department lawyers.
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