WASHINGTON – The sex scandal that led to CIA Director David Petraeus' downfall widened Tuesday with word the top U.S. commander in Afghanistan is under investigation for alleged "inappropriate communications" with another woman involved in the case. Some of the material was "flirtatious," an official said.

Even as the FBI prepared a timeline for Congress about the investigation that brought to light Petraeus' extramarital affair with his biographer, Paula Broadwell, Defense Secretary Leon Panetta revealed that the Pentagon had begun an internal investigation into emails between Gen. John Allen and a Florida woman involved in the case.

Some of the 20,000-plus pages of documents and emails between Allen and Tampa socialite Jill Kelley were "flirtatious," according to a senior defense official who spoke on condition of anonymity because he wasn't authorized to discuss the case publicly. It wasn't immediately clear who wrote the flirtatious notes — Allen, Kelley or both.