WASHINGTON (CNN) -- The CIA destroyed videotapes of interrogations of al Qaeda suspects because they no longer had "intelligence value" and they posed a security risk, CIA director Michael Hayden said Thursday.

CIA Director Michael Hayden says congressional leaders were told about the tapes.

The tapes were made in 2002 and destroyed in 2005, Hayden said in a letter to CIA employees obtained by CNN.

They were made as "an internal check" on the CIA's use of harsh interrogation techniques, believed to include waterboarding, a technique that involves restraining a suspect and pouring water on them to simulate drowning.

The agency made the decision to destroy the tapes "only after it was determined they were no longer of intelligence value and not relevant to any internal, legislative, or judicial inquiries," Hayden said.

"Beyond their lack of intelligence value -- as the interrogation sessions had already been exhaustively detailed in written channels -- and the absence of any legal or internal reason to keep them, the tapes posed a serious security risk," Hayden said. "Were they ever to leak, they would permit identification of your CIA colleagues who had served in the program, exposing them and their families to retaliation from al Qaeda and its sympathizers."

Hayden said he was providing the background information to CIA employees because he expected possible "misinterpretations of the facts in the days ahead." Watch why the tapes' destruction is controversial »

A government official with knowledge of the tapes said the tapes were of al Qaeda operative Abu Zubayda and another detainee.

Hayden said the agency began taping interrogations after the 2002 capture of Zubayda, whose "defiant and evasive" response to "normal questioning ... made imperative the use of other means to obtain the information."

"To meet that need, CIA designed specific, appropriate interrogation procedures," Hayden wrote. "Before they were used, they were reviewed and approved by the Department of Justice and by other elements of the executive branch."

To ensure the interrogations proceeded "in accord with established legal and policy guidelines," the agency began videotaping the questioning. The videotaping began and ended in 2002, Hayden said.

The director said the Office of the General Counsel and the Office of the Inspector General examined the tapes in 2003 and determined the interrogations were lawful. Hayden also said the leaders of the CIA's congressional oversight committees were informed "years ago" of the videos and the agency's intent to destroy them.

"What matters here is that it was done in line with the law," he said. "Over the course of its life, the agency's interrogation program has been of great value to our country. It has helped disrupt terrorist operations and save lives. It was built on a solid foundation of legal review. It has been conducted with careful supervision. If the story of these tapes is told fairly, it will underscore those facts."

U.S. President George W. Bush disclosed the detention of Zubayda in September 2006 and said his behavior prompted the use of "an alternative set of procedures," which he said were cleared by the U.S. Department of Justice.

Information obtained from Zubayda under the new interrogation procedures led investigators to al Qaeda member Ramzi bin al Shibh, Bush said, and information from Zubayda and bin al Shibh led investigators to Khalid Shaikh Mohammed, the mastermind of the September 11, 2001, terror attacks.

Critics have questioned the importance of the information obtained from Zubayda, and the entire question of what type of interrogation techniques are appropriate for use by the United States became a key issue in the confirmation process for Attorney General Michael Mukasey.

Sen. Patrick Leahy, the Vermont Democrat who heads the Senate Judiciary Committee, said news the CIA destroyed the videotapes "is troubling, and it fits a pattern we have seen repeatedly during this administration."

"When an administration abandons the moral high ground to take the low road, they are mortgaging the historic commitment to human rights that is part of the legacy of every American. The damage is compounded when such actions are hidden away from accountability," Leahy said in a statement. E-mail to a friend

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