Retired Gen. David Petraeus, who resigned as CIA director last week after admitting an extramarital relationship, could possibly face military prosecution for adultery if officials turn up any evidence to counter his apparent claims that the affair began after he left the military.

The affair between Petraeus and his biographer, Paula Broadwell, both of whom are married, began several months after his retirement from the Army in August 2011 and ended four months ago, retired U.S. Army Col. Steve Boylan, a former Petraeus spokesman, told ABC News.