WASHINGTON -- The Justice Department is investigating whether Guantanamo Bay detainees charged with roles in the Sept. 11 attacks were improperly given photos of CIA officers or contractors, according to a person familiar with the investigation.

The investigation, headed by the Justice Department's counterespionage chief, John Dion, is trying to determine if military lawyers defending the detainees divulged classified information or compromised covert CIA officers, according to the person, who was not authorized to discuss the investigation and spoke only on condition of anonymity.

It is a violation of federal law to identify CIA covert personnel, and it is a violation of military commission rules to disclose classified information, even if only to the defendants.

The person who spoke to The Associated Press said the photos at issue were provided by the John Adams Project, a combined effort of the American Civil Liberties Union and the National Association of Criminal Defense Lawyers to assist in the defense of the detainees.

The investigation was first reported by The Washington Post on its Web site Thursday night. The ACLU told the Post the organization was confident no laws or regulations had been broken.

The lawyers defending terrorist suspects held at the Navy-run prison at Guantanamo Bay, Cuba, have sought to expose their clients' treatment at the hands of government interrogators, particularly those held in CIA "black sites" overseas, where harsh interrogation tactics were used. Critics of those tactics say they are torture.

Such treatment is likely to play a central role in expected trials for the detainees, either in federal criminal courts or at military commissions, and defense lawyers are expected to try to call CIA personnel and CIA contractors to testify.