The U.S. military aircraft were heading to Bor, the capital of the state of Jonglei and scene of some of the nation’s worst violence over the last week. One American service member was reported to be in critical condition. Officials said after the aircraft took incoming fire, they turned around and headed to Kampala, Uganda. From there the service members were flown on to Nairobi, Kenya for medical treatment, the officials said.

Both officials demanded anonymity to share information not yet made public. Both officials work in East Africa and are in a position to know the information. It was not immediately known what the U.S. aircraft were doing in Bor. One official said it appeared the aircraft were Ospreys, the type of aircraft that can fly like a helicopter and a plane.

Officials at the U.S. military’s Africa Command did not immediately answer phone calls or emails on Saturday.