The Central intelligence Agency (CIA) has destroyed 92 tapes of interviews conducted with terror suspects, a US government lawyer has admitted.
The agency had previously said that it had destroyed only two tapes.
The American Civil Liberties Union (ACLU) has launched a lawsuit against the CIA to seek details of the interrogations of terror suspects.
Techniques involved are understood to have included water-boarding, which the Obama administration says is torture.
The acknowledgment of the 92 destroyed tapes came in a letter sent to the judge presiding over the ACLU lawsuit.
"The CIA can now identify the number of videotapes that were destroyed," the letter by acting US Attorney Lev Dassin, obtained by the BBC, said. "Ninety-two videotapes were destroyed."
Classified?
The letter, dated 2 March, said the CIA was gathering more details for the lawsuit, such as a list of the destroyed records, any secondary accounts describing what was on the destroyed tapes, and the identities of those who may have viewed or possessed the recordings before their destruction.
CIA 'ENHANCED INTERROGATION' TECHNIQUES
Water-boarding: prisoner bound, with cellophane wrapped round his head. Water is poured onto his face and is said to produce a sensation 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
Government lawyers said some of the information may be classified.
"The CIA intends to produce all of the information requested to the court and to produce as much information as possible on the public record to the plaintiffs," the letter said.
In 2005 a judge ordered the preservation of all evidence regarding the treatment of detainees at Guantanamo Bay.
In December 2007, the CIA revealed that two tapes from interviews had been destroyed five months after the ruling.
But the agency said the ruling did not apply to the destroyed tapes, as they concerned interrogations that took place before the suspects had been transferred to Guantanamo.
The agency's chief said the recordings had been made in 2002 as an internal check, and had been erased because they no longer had an intelligence value and could permit identification of CIA officers.
In January 2008, the justice department launched an investigation to answer questions over the tapes.
Tapes were a contentious issue during the trial of 9/11 conspirator Zacaria Moussaoui, who was jailed for his part in the attacks.
Prosecutors initially claimed there were no recordings of his interrogation, but then acknowledged video and audio tapes had been made.
