15 US service members evacuated for treatment after helicopter accident in Syria, defense official says

A total of 15 US service members have been evacuated for treatment after a helicopter accident in Syria on Sunday, including some who are in serious condition, according to a US defense official familiar with the incident.

The service members were taken to Landstuhl Regional Medical Center in Germany, the official said, a major military hospital that for years has treated US troops injured in combat.

Seven other service members were also injured in the accident and treated at the scene, the official said, and some have already returned to duty. All of the troops who sustained injuries are in stable condition, three US defense officials said.

The helicopter involved in the accident was an MH-47 Chinook, a specialized heavy-lift chopper used by special operations forces for movement and operations, according to two defense officials.

The helicopter "had a problem with one rotor that caused a hard landing during takeoff," Pentagon deputy press secretary Sabrina Singh said at a briefing on Tuesday.

"The cause of the incident is under investigation, although no enemy fire was reported," said a statement released by US Central Command on Monday.

The incident occurred at a base in northeastern Syria used by US forces, the officials said, and there were no rescue or recovery efforts taking place outside the compound. The accident occurred during "a period of darkness," a third defense official said, though it was unclear whether it was during an operation.

The cause of the accident is under investigation, CENTCOM said in a statement. US troops in the region have come under fire from hostile forces, including Iranian-backed Shia militias targeting American personnel, but CENTCOM said there was no enemy fire reported in the area during the time of the incident.

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

In April, the US Army grounded all Army aviators not involved in critical missions following two separate helicopter crashes that left 12 soldiers dead.

In one incident, three soldiers died after a mid-air collision of two AH-64 Apache helicopters near Fort Wainwright, Alaska. 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 same month, nine soldiers were killed when two HH-60 Black Hawk helicopters with the 101st Airborne Division crashed in southwestern Kentucky. The two aircraft were conducting a training flight at the time of the crash.

Asked about the accident on Tuesday during a media roundtable, Army Chief of Staff Gen. James McConville said the crash in Syria was different from the incidents that resulted in the stand down.

"We have the world's greatest special operations aviators, quite frankly, no one can do what they do," McConville said. "And they fly at a level that no one else in the world can do. And they do high risk all the time. And sometimes things go wrong when that happens."

CNN's Sandi Sidhu contributed reporting.