The Marine Corps said in a tweet that an active search and rescue operation was underway for service members involved in an aviation "mishap". The Osprey was in Australia for a joint training exercise between the USA and Australia that ended July 25.
"The exercise was to prove (Australian personnel) could operate a broad a range of aircraft", commander Adrian Capner said.
The service members went missing after what the Marine Corps is calling a "mishap" with an MV-22 aircraft, also known as an Osprey heli-plane.
Three people are reported to be missing, feared dead, while up to 20 people have been rescued, according to the Courier-Mail.
Twenty-three of them have been rescued, but a search and rescue effort for the remaining three.
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The helicopter involved in the incident-the MV-22 Osprey-has been the subject of controversy in the past for a shaky safety record and a series of crashes that resulted in the deaths of 39 people over 26 years.
'I can confirm no Australian Defence Force personnel were on board the aircraft, ' Ms Payne said in a statement. Last December, a USA military Osprey crash-landed off Japan's southern island of Okinawa.
She said she had spoken to United States defence secretary James Mattis "to offer Australia's support in any way that can be of assistance".
Four Bell-Boeing MV-22 Osprey aircraft were in Australia from US Marine Medium Tiltrotor Squadron 268, landing in Darwin at the end of April. The Talisman Sabre exercise, a biennial event between the two nations, involved more than 30,000 troops and 200 military aircraft.
The Marine Corps did not say what caused the crash but indicated it is under investigation.