WASHINGTON  The Defense Department is conducting an extensive review of the videotaping of interrogations at military facilities from Iraq to Guantánamo Bay, and so far it has identified nearly 50 tapes, including one that showed what a military spokesman described as the forcible gagging of a terrorism suspect.

The Pentagon review was begun in late January after the Central Intelligence Agency acknowledged that it had destroyed its own videotapes of harsh interrogations conducted by C.I.A. officers, an action that is now the subject of criminal and Congressional investigations.

The review was intended in part to establish clearer rules for any videotaping of interrogations, Defense officials said. But they acknowledged that it had been complicated by inconsistent taping practices in the past, as well as uncertain policies for when tapes could be destroyed or must be preserved.

The officials said it appeared that only a small fraction of the tens of thousands of interrogations worldwide since 2001 had been recorded.