Fox News reports that the U.S. has yet to verify who was responsible for the attack, which targeted a base known as Green Village in northeastern Syria, according to CENTCOM. There have been several attacks on U.S. forces in Syria in recent months, varying from drone-carried explosives to infantry assaults.

"Three 107mm rockets targeted the base. A fourth rocket along with rocket tubes was found at the launch point, approximately 5 kilometers away," CENTCOM wrote in a statement. "U.S. forces in northeast Syria are investigating the incident."