CIA interrogators conducted mock executions of terror suspects and in one case threatened a detainee suspected in the USS Cole bombing with a gun and power drill, according to a report due to be released on Monday.
The disclosures are contained in a secret 2004 report by the CIA's inspector general which a federal judge has ordered to be made public on Monday in response to a Freedom of Information Act lawsuit filed by the American Civil Liberties Union (ACLU).
In one case, interrogators brought a gun and power drill into a session with suspected Cole bomber Abd al Rahim al-Nashiri, the report says. The suicide bombing of the warship USS Cole killed 17 US sailors in Yemen in 2000.
In another episode, a gunshot was fired in a room next to a detainee to make the prisoner believe another suspect had been killed, according to the report.
Nashiri was one of three CIA prisoners subjected to waterboarding, a brutal interrogation technique that simulates drowning that was among 10 techniques approved by the Bush administration's Justice Department in 2002. President Barack Obama and Attorney General Eric Holder have denounced waterboarding as torture.
"The CIA in no way endorsed behavior - no matter how infrequent - that went beyond formal guidance," said agency spokesman Paul Gimigliano. He declined to comment on the contents of the IG report.
Threatening a prisoner with death violates US anti-torture laws.
Holder is considering whether to appoint a criminal prosecutor to investigate the Bush administration's interrogation practices, a controversial move that would run counter to President Barack Obama's wishes to leave the issue in the past.
Mr Gimigliano said the career prosecutors at the Justice Department have reviewed the report to determine if any laws were broken and whether the interrogators should be prosecuted.
"Professionals in the Department of Justice decided if and when to pursue prosecution," he said. "That's how the system was supposed to work, and that's how it did work."
Just one CIA contract interrogator, David Passaro, has been prosecuted. He was found guilty in 2007 of beating a prisoner to death in Afghanistan.
The Los Angeles Times reported Aug. 9 that a CIA operative brought a gun into an interrogation booth to force a detainee to talk. One of the congressional officials told the AP that referred to the interrogation of the USS Cole suspect.
The IG review was completed in May 2004. The ACLU has sought its release since then. It was expected to be released earlier this year but was delayed by government request.
The IG review cast doubt on the effectiveness of the harsh interrogation methods employed by CIA interrogators, according to quotes from the report that were contained in Bush-era Justice Department memos declassified this spring. It says no attacks were averted by information obtained using harsh interrogation methods.
The CIA detained and interrogated 94 terrorist suspects; 28 were subjected to harsh methods. Of those three were waterboarded, according to government documents made public earlier this year.
But former CIA Director Michael Hayden said this week at a panel discussion in Washington that the review also credits the harsh interrogation with yielding information on al-Qaeda's basic infrastrucutre, which in turn allowed the CIA to fight the organization behind the 9/11 hijackings.
John L. Helgerson, the now-retired CIA inspector who spearheaded the investigation, said in June that the report is a comprehensive review of everything the CIA did in the secret detention and interrogation program begun in the wake of the Sept. 11 terrorist attacks.
The investigation was undertaken in response to concerns expressed by agency employees about the program, he added.
AP