Twenty-two U.S. service members aboard a Special Operations Forces helicopter were injured Sunday at a U.S. base in northeastern Syria, said two Defense officials Tuesday.
The troops were landing at a staging base during a special operations mission when their MH-47 Chinook helicopter experienced an apparent mechanical issue, according to the officials.
A structure was slightly damaged by the helicopter.
No enemy fire was reported, the military command said in a brief statement.
Fifteen of those injured were evacuated to Landstuhl Regional Medical Center, the U.S. Army hospital near the U.S. Air Force base in Ramstein, Germany for treatment, said one official. One of the injured was sent to the U.S.
The second official said all of the injured service members are currently in stable condition and some have already returned to work.
The incident is under investigation by the Army.
U.S. forces are operating in Syria to fight the Islamic State terrorist group.
Central Command said this month that it and partner forces carried out 17 operations in Syria in May that killed two Islamic State operatives and led to the detention of 20 others. Central Command has said its local partners in the country are the Syrian Democratic Forces.
A civil war broke out in Syria in 2011. The United Nations estimated last year that more than 306,000 civilians have been killed since the conflict began. More than 12 million have been displaced, either internally within Syria or outside the country, according to the U.N.'s refugee agency.