The C.I.A. would not identify the officer, but several government officials said it was Mary O. McCarthy, a veteran intelligence analyst who until 2001 was senior director for intelligence programs at the National Security Council, where she served under President Bill Clinton and into the Bush administration.

At the time of her dismissal, Ms. McCarthy was working in the agency's inspector general's office, after a stint at the Center for Strategic and International Studies, an organization in Washington that examines global security issues.

The dismissal of Ms. McCarthy provided fresh evidence of the Bush administration's determined efforts to stanch leaks of classified information. The Justice Department has separately opened preliminary investigations into the disclosure of information to The Post, for its articles about secret prisons, as well as to The New York Times, for articles last fall that disclosed the existence of a program of domestic eavesdropping without warrants supervised by the National Security Agency. Those articles were also recognized this week with a Pulitzer Prize.

The leak pertained to stories on the CIA’s rumored secret prisons in Eastern Europe, sources told NBC. The information was allegedly provided to Dana Priest of the Washington Post, who wrote about CIA prisons in November and was awarded a Pulitzer Prize on Monday for her reporting.

Sources said the CIA believes McCarthy had more than a dozen unauthorized contacts with Priest. Information about subjects other than the prisons may have been leaked as well.