The US justice department and the CIA are launching a joint inquiry into the CIA's destruction of two videotapes of interrogations of al-Qaeda suspects.
The CIA said the tapes no longer had any "intelligence value"
CIA chief General Mike Hayden said the agency would co-operate fully with the preliminary inquiry, to decide whether a full investigation is necessary.
Democrats have accused the CIA of a cover-up to hide evidence of possible torture and abuse of detainees.
The CIA says it destroyed the tapes to protect the identity of its agents.
Justice Department officials, lawyers from the CIA general counsel's office and the CIA inspector general are expected to begin their inquiry early this week.
In a statement, Gen Hayden welcomed the move, describing it as "an opportunity to address questions that have arisen over the destruction back in 2005 of videotapes".
The White House had no immediate comment on the decision.
In an earlier internal memo to CIA employees, Gen Hayden said the CIA had begun taping interrogations as an internal check in 2002 and decided to delete the videos because they no longer had "intelligence value" and posed a security risk.
President George W Bush has said he has "no recollection" of the tapes' existence and was not aware of the plan to destroy them.
The inquiry follows angry calls by leading Democrats for a criminal investigation into the CIA's actions.
CIA 'ENHANCED INTERROGATION' TECHNIQUES
Water boarding: prisoner bound to a board with feet raised, and cellophane wrapped round his head. Water is poured onto his face and is said to produce a fear of drowning
Cold cell: prisoner made to stand naked in a cold, though not freezing, cell and doused with water
Standing: Prisoners stand for 40 hours and more, shackled to the floor
Belly slap: a hard slap to the stomach with an open hand. This is designed to be painful but not to cause injury
Source: Described to ABC News by un-named CIA agents in 2005
Senator Dick Durbin, the second most powerful Democrat in the Senate, called on the US attorney general to investigate whether CIA officials had violated the law.
Others accused the CIA of a cover-up and described the CIA's explanation as "a pathetic excuse".
"The past six years, the Bush administration has run roughshod over our ideals and the rule of law," said veteran Democratic Senator Edward Kennedy.
"Now, when the new Democratic Congress is demanding answers, the administration is feverishly covering up its tracks," he said.
The House and Senate Intelligence Committee are beginning their own inquiries.
The CIA revelation has also drawn criticism from civil liberties and human rights groups.
The Human Rights Watch said the wiping of the tapes was "destruction of evidence", and described the reasons given by the CIA as "disingenuous".
Michael Hayden wrote to all CIA employees about the tapes
The American Civil Liberties Union accused the agency of showing an utter disregard for the law.
Correspondents say the news is likely to trigger more questions about the interrogation techniques used by the CIA and whether they amount to torture.
The techniques are alleged to have included water-boarding, a method in which a suspect is made to feel he is drowning.
Human rights groups say that water-boarding - and other techniques allegedly used by the CIA - can be defined as torture under various international treaties to which the US is a signatory.
The Bush administration has always maintained that it does not allow the use of torture.
The tapes are thought to have shown the interrogation in 2002 of a number of terror suspects, including Abu Zubaydah, who had been a chief recruiter for the al-Qaeda network.