The service members’ unit came in contact with enemy forces. That’s when the casualties occurred, a U.S. military official told CNN. “There is the possibility that fratricide may have been involved,” he said. The incident is under investigation.

A NATO statement provided similar information.

Roghliwanai said the troops had completed their joint military sweep when they came under rocket fire from Taliban militants.

The service members called in air support. “But the airstrike mistakenly bombed their own friends too,” he said.