The Pentagon says the top American commander in Afghanistan is under investigation for alleged "inappropriate communications".
Marine General John Allen, who served until 2008 at Camp Lejeune, is being investigated for emails with Jill Kelley, the woman who is said to have received threatening emails from Paula Broadwell, the woman with whom former CIA Director David Petraeus had an extramarital affair.
A senior Defense Department official says the emails between Allen and Kelley were "flirtatious."
Defense Secretary Leon Panetta says the FBI referred the matter to the Pentagon on Sunday. Panetta says he ordered a Pentagon investigation of Allen on Monday.
Kelley is a close friend of Petraeus' and served as a sort of social ambassador for U.S. Central Command in Tampa, hosting parties for the general when he was commander there from 2008-10. The 37-year-old woman's complaint about an anonymous, threatening email triggered an FBI investigation that uncovered Petraeus' affair and led to his downfall.
Petraeus resigned as CIA director on Friday.
Allen served as deputy commanding general with the II Marine Expeditionary Force and commanding general of the 2d Marine Expeditionary Brigade from 2006 to 2008 while at Camp Lejeune.