Immediately after The Washington Post revealed last week that the US Central Intelligence Agency (CIA) has been operating a secret prison system abroad, the spy agency sent a report to the Justice Department requesting a review of the story to determine whether classified information was leaked.

The action by CIA's general counsel was taken immediately after the Washington Post article was published on Nov. 2, CNN reported Tuesday, quoting an official.

The move was similar to the one taken when CIA's undercover agent Valerie Plame's identity was made public in July 2003.

By law, when there is the possibility that classified information has been leaked, the CIA is required to inform the Justice Department, which generally launches an investigation into the matter, the CNN report said.

The CIA's referral was the first step toward a full-scale criminal investigation of a leak of possibly classified information on secret prisons abroad, the Associated Press quoted an anonymous official as saying.

The Justice Department will decide whether to initiate a criminal investigation.

The Washington Post reported last week that the CIA was operating covert detention centers in eight foreign countries for holding suspected terrorists.

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

The existence and locations of these prisons - referred to as "black sites" in classified governmental documents - are known only to 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 Washington Post report.

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

In a draft letter addressed to the chairmen of the Senate and the intelligence committees, 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-term and 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.

Source: Xinhua