Twenty-two US service members have been injured to "various degrees" after a "helicopter mishap" in northeastern Syria, according to a statement released by US Central Command on Monday.

"The cause of the incident is under investigation, although no enemy fire was reported," the statement said.

The service members are receiving treatment for injuries and 10 have been evacuated to higher care facilities.

Additional details were not immediately provided.

In April, the US Army grounded all Army aviators not involved in critical missions following two helicopter crashes that left 12 soldiers dead. The safety stand down came after a mid-air collision of two AH-64 Apache helicopters near Fort Wainwright, Alaska, that killed three soldiers and wounded another. Two of the soldiers died at the scene and the third died while being transported to a hospital, according to a release from the US Army's 11th Airborne Division.

The US has approximately 900 troops in Syria as part of the ongoing mission to defeat ISIS.