WASHINGTON, Nov. 8 (Xinhuanet) -- Two leaders in the US Congress are calling for an investigation into the leak of the secret prison system overseas run by the Central Intelligence Agency (CIA).

    Senate Majority Leader Bill Frist and House of Representatives Speaker Dennis Hastert in a draft letter asked the Congress's intelligence committees to "immediately initiate a joint investigation into the possible release of classified information."

    The draft letter, addressed to the chairmen of the Senate and House intelligence committees, was first reported by the Associated Press.

    The Washington Post reported on Nov. 2 that the CIA was operating covert detention centers in eight foreign countries for holding terror suspects.

    The report said the prison system was set up nearly four years ago and included detention centers in Afghanistan, several Eastern European countries as well as the US naval base in Guantanamo Bay,Cuba.

    The existence and locations of these prisons - referred to as "black sites" in classified governmental documents - are known to only a handful of officials in the United States and, usually, only to the president and a few top intelligence officers in each host country, according to the newspaper.

    The Bush administration has not confirmed or denied the report.

    In their draft letter, Frist and Hastert said they wanted the intelligence committees to investigate if the information about the secret prison system was classified and accurate, who leaked it and under what authority.

    "If accurate, such an egregious disclosure could have long-termand far-reaching damaging and dangerous consequences, and will imperil our efforts to protect the American people and our homeland from terrorist attacks," the draft letter said. Enditem