The FBI is conducting investigations similar to the one that resulted in last week's firing of a senior CIA analyst who acknowledged leaking classified information, director Robert Mueller said Monday.

"We do have investigations going," Mueller said following a visit to the FBI's Charlotte office, which oversees the agency's operations in North Carolina. "Leaking of classified materials is a concern for those agencies that have classified materials."

Mary McCarthy, who was nearing retirement at the CIA, has been identified as being fired after leaking information that resulted in the story last year in The Washington Post disclosing a network of secret CIA prisons in eastern Europe. The Post won a Pulitzer Prize last week for its report.

One law enforcement official said last week that dozens of leak investigations were under way. The official spoke on condition of anonymity because the matter is under investigation.

Justice Department officials would not comment publicly on the CIA firing or say if the matter had been referred to prosecutors for possible criminal charges.

Speaking to the Anti-Defamation League on Monday in Washington, National Intelligence Director John Negroponte did not mention the firing of the CIA officer. A reporter shouted a question to him about the issue as he left, but he did not stop to reply. Negroponte has condemned leaks in the past.

Mueller also said last month's attack at the University of North Carolina at Chapel Hill, where an SUV was driven through a popular campus gathering spot, illustrates the need for vigilance against terrorism.

"As it is all over the country, you have instances of people taking matters into their own hands," Mueller said, citing the need for the FBI to continue intense efforts to uncover such activity.

No one was seriously injured in the attack. Mohammed Reza Taheri-azar, a 22-year-old native of Iran who graduated from UNC-Chapel Hill in December, has been charged with nine counts of attempted murder and assault with a deadly weapon.

Taheri-azar has said the attack was meant as revenge on the U.S. government for the deaths of Muslims around the world. The FBI is continuing to investigate.