The officials told Tuesday's Los Angeles Times a Predator drone fired the missile that killed a Marine and a medic last week.
Marine Staff Sgt. Jeremy D. Smith of Arlington, Texas, and Seaman Benjamin D. Rast of Niles, Mich., were apparently mistaken for insurgents moving to attack another group of Marines in the area.
"With increased (drone) usage, there are going to be more incidents like this," said Louis Tucker, the former staff director for the Senate Intelligence Committee.
Tucker said people mistakenly think there won't be any mistakes because drones are automated.
"That's never the case in war," he said.
Drones have been involved in airstrikes that accidentally killed Afghan and Pakistani citizens since the U.S. began using them a decade ago.
Last week's incident appeared to be the first case of U.S. troops being hit by "friendly fire" from drone aircraft.