Three US Marines have been killed and several others seriously wounded after an Osprey aircraft crashed during military exercises in Australia.

Of the 23 Marines on board the MV-22B Osprey aircraft, three died while five others have been transferred to Royal Darwin Hospital in a serious condition, the Marine Rotational Force – Darwin said in a statement on Sunday.

The incident on Melville Island happened at 9:30 a.m. local time.

“The Marines aboard the aircraft were flying in support of Exercise Predators Run. Recovery efforts are ongoing,” the statement read, adding “the cause of the incident is under investigation.”

Earlier, Northern Territory Chief Minister Natasha Fyles said some of the other Marines were being treated at the scene.

“We are working incredibly hard and as fast as we can to make sure we can get people to treatment,” Fyles said.

After an incident like this, it’s common for an operational stand-down to be announced, when officials ground a fleet of aircraft while they perform an accident investigation, CNN military analyst and retired US Air Force Col. Cedric Leighton said Sunday on “CNN This Morning.”

Leighton said it’s too soon to say whether the accident was due to a mechanical failure or some other issue.

Source: CNN