At the CIA's request, the Justice Department is weighing whether to open a criminal investigation into the leak of possibly classified information on secret prisons to The Washington Post.

A story the newspaper published on Nov. 2 touched on a number of sensitive national security issues, including the existence of secret CIA detention centers for suspected terrorists in Eastern European democracies.

A U.S. official, speaking on condition of anonymity because the issue deals with classified information, said the CIA's general counsel made the referral to the Justice Department shortly after the story appeared last week.

The department will decide whether to initiate a criminal investigation. The leak investigation into the disclosure of covert CIA officer Valerie Plame's identity came about through the same referral procedure and led to a five-count indictment against the vice president's now former chief of staff, I. Lewis Libby.

Post spokesman Eric Grant said Tuesday the newspaper had no comment.

Secretary of State Condoleezza Rice sidestepped questions about possible secret prisons, saying the United States was in a "different kind of war" and had an obligation to defend itself.

"We, our allies, others who have experienced attacks, have to find a way to protect our people," said Rice, who would not confirm the existence of secret prisons.

On Capitol Hill, Senate Majority Leader Bill Frist, R-Tenn., and House Speaker Dennis Hastert, R-Ill., called for a congressional investigation into the disclosure of the existence of the secret prisons.

If the Post story is 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 lawmakers wrote while asking for a joint leak probe by the Senate and House intelligence committees.

The letter was written to Senate Intelligence Committee Chairman Pat Roberts, R-Kan., and his House counterpart, Intelligence Committee Chairman Peter Hoekstra, R-Mich.

Concerning the leak of information about prisons, the letter asked, "What is the actual and potential damage done to the national security of the United States and our partners in the global war on terror?"

The newspaper's story said the CIA has been hiding and interrogating some of its most important Al Qaeda captives at a Soviet-era compound in Eastern Europe, part of a covert prison system set up by the agency four years ago that at various times has included sites in eight countries. Those countries, the Post said, include several democracies.

The allegations prompted denials from governments in the former Soviet bloc. Such prisons, European officials say, would violate the continent's human rights principles.

"If the leadership determines that we should investigate the leak, it would be much like the 9/11" commission, Roberts said. The Intelligence Committee chairman did not dispute a reporter's suggestion that a probe would raise First Amendment press-freedom issues.

Such an investigation would become "very difficult when you're getting into matters like this," the senator said.

Roberts also said he would support hearings into the importance of maintaining a covert agent's cover, a topic triggered by the leak of Plame's identity, eight days after her husband accused the Bush administration of manipulating prewar intelligence to exaggerate the Iraq threat.

Democratic leader Harry Reid of Nevada said the House and Senate committees with normal jurisdiction should conduct any hearings, not a bicameral committee as suggested in the letter of the two Republican leaders.

House Minority Leader Nancy Pelosi, D-Calif., said any such joint investigation should also investigate possible manipulation of prewar intelligence on Iraq.

"If Speaker Hastert and Majority Leader Frist are finally ready to join Democrats' demands for an investigation of possible abuses of classified information, they must direct the House and Senate Intelligence Committees to investigate all aspects of that issue," Pelosi said.

Kenneth Roth, executive director of Human Rights Watch, said Republicans "should be focused on the illegality of these prisons, not the revelation of the illegality."