In a statement, Capt. Bryan L. Bouchard says the MQ-9 Reaper went down at Kandahar Airfield late Saturday.
He says the cause is under investigation "but hostile fire was not a factor."
Kandahar Airfield, the largest base in Afghanistan, is being renovated by the U.S.-NATO mission for mixed military and civilian use.
Suicide bomb in southern Afghanistan, kills at least 20