"As has happened recently, when lapses occur, they have the potential to erode public confidence in our leadership and in our system for the enforcement of high ethical standards," Panetta wrote. "Worse, they can be detrimental to the execution of our mission to defend the American people."
Panetta didn't mention Petraeus in the memo, and the defense chief's spokesman said the request for an ethics review was in the works before the Petraeus matter came to light.
Petraeus, in his first media interview since he resigned, told CNN that he had never given classified information to Broadwell. He also said his resignation had nothing to do with his upcoming testimony to Congress about the attack on the U.S. Consulate and CIA base in Benghazi, Libya, that caused the death of four Americans.
He told the network he wanted to testify about the Libya matter. And he'll have that opportunity on Friday, when he appears before the House Intelligence Committee. Committee officials planned to limit the subject of that hearing to Libya, ruling out questioning about the affair with Broadwell and any potential national security implications.
Both Petraeus and Broadwell have said she didn't get any classified documents from him. But the FBI has found a substantial number of classified documents on her computer and in her home, according to a law enforcement official. That official spoke only on condition of anonymity because the official was not authorized to speak publicly about the case.
Broadwell, a former Army intelligence officer, has told agents that she took classified documents out of secure government buildings. The Army has now suspended her security clearance.
Asked why the Justice Department did not inform the president and Congress regarding the investigation involving Petraeus, Attorney General Eric Holder said Thursday, "As we went through the investigation and looked at the facts and tried to examine them as they developed, we felt very secure in the knowledge that a national security threat did not exist."
Had there been a security threat, "we would of course have made that known to the president and also to the appropriate members on the Hill," the attorney general said at a New Orleans news conference on another topic.
In the absence of such a threat, "we do not share outside the Justice Department, outside the FBI the facts of ongoing investigations," he added. He said the department does not share information from criminal investigations so that such probes "can be seen as being done in an impartial way."
Holder also said that "a very critical interview" took place Nov. 2, the Friday before Election Day, and that afterward, the Justice Department thought it appropriate to share information with top Obama administration officials.
A federal law enforcement official said that Friday interview was with Broadwell and that the questioning reassured FBI agents that they knew what classified documents Broadwell had, where they came from and that they had not come from Petraeus.
It was a case of the agents becoming satisfied that they knew the complete story about the origin, range and scope of documents involved, according to this official, who demanded anonymity in order to discuss an ongoing case. On Nov. 6, the FBI informed National Intelligence Director James Clapper of the investigation.
The sales ranking of Broadwell's biography of Petraeus rose in the 24 hours after his resignation from 76,792 on Amazon to 111, but it had dropped to 280 as of Thursday.
Burns reported from Bangkok. Associated Press writers Kimberly Dozier, Adam Goldman, Lolita C. Baldor, Pete Yost and Donna Cassata contributed to this report.
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