The officer, Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff, told reporters that secondary explosions after the drone strike last Sunday supported the military’s conclusion that the car contained explosives — either suicide vests or a large bomb. General Milley said that military planners took proper precautions beforehand to limit risks to civilians nearby.

But the military’s preliminary analysis of the strike and the circumstances surrounding it offer much less conclusive evidence to support those claims, military officials acknowledge. It also raises questions about an attack that friends and family members of the car’s driver say killed 10 people, seven of them children.

So far, there is no ironclad proof that explosives were in the car. The preliminary analysis says it was “possible to probable” that was so, according to officials who have been briefed on the assessment. Drone operators and analysts scanned the cramped courtyard where the sedan was parked for just a few seconds. Seeing no civilians, officials said, a commander ordered the strike, only for a grainy live-video feed to show other figures approaching the vehicle seconds later as the Hellfire missile raced closer to its target.