The top American commander in Afghanistan is now under investigation in connection with the Gen. David Petraeus sex scandal.
The Pentagon says General John Allen, Commander of the International Security Assistance Force (ISAF) in Afghanistan is accused of "inappropriate communications" with the woman who says she received threatening emails from Petraeus' mistress.
Secretary of Defense Leon Panetta said in a written statement that the FBI referred the matter to the Defense Department on Sunday.
Panetta said: "Today, I directed that the matter be referred to the Inspector General of the Department of Defense for investigation, and it is now in the hands of the Inspector General. I have informed the Chairman and Ranking Member of the Senate Armed Services Committee. The House Armed Services Committee has also been notified."
A senior defense official traveling with Panetta told the Associated Press that Allen's communications were with Jill Kelley, who has been described as an unpaid social liaison at MacDill Air Force Base, Fla., which is headquarters to the U.S. Central Command. She is not a U.S. government employee.
It is unclear what Allen's communications contained.
Kelley is said to have received threatening emails from Paula Broadwell, who is Petraeus' biographer and who had an extramarital affair with Petraeus that reportedly began after he became CIA director in September 2011.
Petraeus resigned as CIA director on Friday.
Allen, a four-star Marine general, succeeded Petraeus as the top American commander in Afghanistan in July 2011.
Allen's nomination to be the next commander of U.S. European Command and the commander of NATO forces in Europe has been put on hold.
Panetta said: "In the meantime, I have asked the President - and the President has agreed - to put his nomination on hold until the relevant facts are determined. I have asked both Senators Levin and McCain that the confirmation hearing on General Allen's pending nomination to be Commander of United States European Command and Supreme Allied Commander, Europe be delayed."