Washington - The Senate Intelligence Committee is preparing to launch an investigation of the CIA's detention and interrogation programs under President Bush, setting the stage for a sweeping examination of some of most secretive and controversial operations in recent agency history.

    The probe is aimed at uncovering new information on the origins of the programs as well as scrutinizing how they were executed -- from the conditions at clandestine CIA prison sites to the interrogation regimens used to break Al Qaeda prisoners, according to Senate aides familiar with the inquiry plans.

    Officials said the inquiry is not designed to determine whether CIA officials broke laws. "The purpose here is to do fact-finding in order to learn lessons from the programs and see if there are recommendations to be made for detention and interrogations in the future," said a senior Senate aide, who like others, described the plans on condition of anonymity because they have not been made public.

    Still, the investigation is likely call new attention to the agency's conduct in operations that drew condemnation around the world. It is also bound to renew friction between Democrats and Republicans who have spent much of the last five years fighting over the Bush administration's prosecution of the war on terrorism.

    The investigation also could draw comparisons to the special Senate committee formed to investigate the CIA in 1975 and headed by Sen. Frank Church, an Idaho Democrat. Revelations by the Church Committee led to greater congressional oversight and legislation restricting intelligence activities.

    The terms and scope of the new inquiry still were being negotiated by members of the committee and senior staffers Thursday. The senior aide said the committee had no short-term plans to hold public hearings, and that it was not clear whether the panel would release its final report to the public.

    The inquiry, which could take a year or more to complete, means the CIA will once again be the target of intense congressional scrutiny at a time when it is engaged in two wars and its ongoing pursuit of Al Qaeda.

    The agency was been stripped of some of its power and prestige after coming under severe criticism in previous investigations of its failures leading up to the Sept. 11 attacks and the war in Iraq.

    But whereas those investigations focused largely on errors in the CIA's analytic efforts, the new probe will dive directly into its most sensitive operations, seeking to unearth details that previous generations of agency officials referred to as the "crown jewels."

    During the Bush administration, the agency was often able to safeguard many of those secrets. Lawmakers have never been told the locations of the CIA's secret prisons overseas, for example.

    But the Obama administration is expected to give congressional investigators new access to classified records as well as individuals who took part in operating the secret prisons and interrogating detainees.

    CIA Director Leon E. Panetta pledged this week that he would cooperate with any congressional probe.

    "If those committees are seeking information in these areas, we'll cooperate with them," Panetta said in a meeting with reporters Wednesday. "I think that we have a responsibility to be transparent on these issues and to provide them that information."

    Panetta argued that CIA officers should not face prosecution if they were acting on orders in accordance with Bush administration legal opinions.

    "I would not support, obviously, an investigation or a prosecution of those individuals," Panetta said. "I think they did their job, they did it pursuant to the guidance that was provided them, whether you agreed or disagreed with it."

    News of the probe was greeted with concern among agency veterans.

    "There is a good deal of investigation fatigue, and a feeling that the agency has become even more than before a piñata," said a former high-ranking CIA official, who spoke on condition of anonymity.

    The new investigation is likely to "stimulate more risk aversion," the former official said. "There's a potential cost to other operations down the road when the current administration says, 'We would like you to take this operation, it's been blessed by lawyers and briefed by Congress.' Why should we do anything anywhere near cutting-edge if down the road the next administration can decide to get back at their political opponents?"

    Senate aides declined to say whether the committee would seek new testimony from former CIA Director George J. Tenet or other former top officials who were involved in the creation and management of the programs.

    The Senate probe will examine whether the detention and interrogation operations were carried out in ways that were consistent with the authorities and instructions issued in the aftermath of the Sept. 11 attacks, officials said.

    The panel will also look at whether lawmakers were kept fully informed. Sen. Dianne Feinstein (D-Calif.), the chairwoman of the committee, and others have said that the Bush administration improperly withheld information from Congress on the CIA's operations.

    The investigation comes at a time when the Obama administration is in the midst of making dramatic changes in the CIA's counter-terrorism programs.

    Last month, Obama ordered the CIA to close its secret prison facilities and to abandon "enhanced" interrogation measures, including waterboarding, a method that simulates drowning. Instead, Obama ordered the agency to abide by the Army Field Manual on interrogation.

    The administration has also established a task force to look at the interrogation programs, although that effort is mainly designed to examine their effectiveness and determine whether the CIA should again be granted authority beyond the Army Field Manual.

    Senate investigators plan a similar line of inquiry, with a goal of assessing the effectiveness of enhanced interrogation techniques employed by the CIA, including sleep deprivation and subjecting prisoners to cold temperatures.

    Former CIA Director Michael V. Hayden has defended the agency's use of such methods and argued that the agency should not be bound by the constraints of the Army Field Manual.

    Hayden has said that the agency had held fewer than 100 prisoners in custody since the Sept. 11 attacks, and that less than one-third of those were ever subjected to enhanced interrogation measures. Three prisoners, including self-proclaimed Sept. 11 mastermind Khalid Shaikh Mohammed, were subjected to waterboarding.

    There has also been a push from other lawmakers to launch an independent investigation of the CIA's operations. The Senate Judiciary Committee has scheduled a hearing next week on a proposal to create a commission like the one that investigated the Sept. 11 attacks to examine CIA counter-terrorism operations under Bush.

    "The last administration justified torture, presided over the abuses at Abu Ghraib, destroyed tapes of harsh interrogations," said Sen. Patrick J. Leahy (D-Vt.), the chairman of that committee. "How can we restore our moral leadership and ensure transparent government if we ignore what has happened?"

    But the Senate Intelligence Committee has direct jurisdiction over U.S. spy agencies, and is launching its probe in part to make sure its members have independent data and are in position to influence future interrogation and detention policies, officials said.

    Aides said the negotiations were aimed at producing a probe with broad support from members of both parties. Republicans have argued that the investigation be focused on CIA programs and not become a referendum on Bush administration policies, such as the Justice Department legal memos that underpinned the program.

    Sen. Christopher S. Bond (R-Mo.), the ranking Republican on the committee, "does not think that witch hunts and discussions of the legality of [Justice Department] memos are in any way helpful at this point," another Senate aide said.