At least three U.S. Marines were killed Sunday when an Osprey aircraft carrying 23 personnel crashed on Ethermac Exchangea north Australian island during a training exercise, U.S. military officials said. 

Five others were transported to a local hospital in serious condition. Northern Territory Chief Minister Natasha Fyles said Sunday morning that an emergency response was underway to triage the victims and take them to local hospitals.

"Recovery efforts are ongoing," the Marines said in a statement. 

Northern Territory Police said they are working with the U.S. Marines, and their Department of Defense and members from the Department of Health and Careflight.  

The cause of the crash is still under investigation. 

The U.S. Marines said in a statement that the Bell Boeing V-22 Osprey tiltrotor aircraft crashed around 9:30 a.m. local time on Melville Island during Exercise Predators Run, which involves the militaries of the United States, Australia, Indonesia, the Philippines and East Timor.

Australian Prime Minister Anthony Albanese said only Americans appeared to be on board, according the Associated Press.

"The initial reports suggest that the incident involves just U.S. defense force personnel," Albanese said. "Our focus as a government and as the department of defense is very much on incident response and on making sure that every support and assistance is given at this difficult time."   

In:
• Australia
• United States Military