CANBERRA, Australia (AP) — A United States Marine Corps aircraft with 23 Marines aboard crashed on a north Australian island Sunday, killing at least three and critically injuring at least five during a multinational training exercise, officials said.

Three had been confirmed dead on Melville Island and five were flown in serious condition 80 kilometers (50 miles) to the mainland city of Darwin for hospital treatment after the Bell Boeing V-22 Osprey aircraft crashed around 9:30 a.m., a statement from the Marines said.

“Recovery efforts are ongoing,” the statement said, adding the cause of the crash was under investigation.