Canberra: A United States Marine Corps helicopter V-22 Osprey, carrying about 23 marines, crashed during the Predators Run exercises off the coast of the northern Australian city of Darwin, killing three Marines and injuring 20 media reported.

The helicopter crash occurred at 01:30 GMT near Melville Island, the broadcaster reported, adding that the incident may have killed people, as some personnel remain missing.

“Three had been confirmed dead on Melville Island and five of the 23 on board 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 tiltrotor aircraft crashed around 9:30 a.m.,” AP reported citing a statement from the Marines.

The military drills, which involve military from the United States, Australia, Indonesia, the Philippines, and Timor-Leste, will be suspended due to the crash, according to reports

A rescue operation is underway. “Recovery efforts are ongoing,” the statement said, adding the cause of the crash was under investigation.

Australian Prime Minister Anthony Albanese called the incident a “tragic” one.

A U.S. military official reported to Australian air traffic controllers a “significant fire in the vicinity of the crash site,” according to an audio recording of the conversation broadcast by Nine News television, stated the AP report.