WASHINGTON – The CIA said Thursday that it had opened an “exploratory” investigation into the conduct of former director David Petraeus, who resigned after admitting to adultery, and Defense Secretary Leon Panetta ordered the military services to consider how to strengthen ethics standards “that keep the military well led and well disciplined.”

The CIA and Pentagon reviews stem from the resignation of Petraeus, a retired Army general, and revelations that Marine Corps Gen. John Allen exchanged possibly inappropriate emails with the woman who triggered the FBI investigation that exposed Petraeus’ affair.

The military also has been rattled by a slew of lesser-known, more serious cases, including a general recalled from Afghanistan who is facing criminal charges of sexually assaulting or committing adultery with five women. The Pentagon, however, said the timing of Panetta’s directive was “coincidental.”