The defence force has promised to bring home “our four mates” as grave fears are held for the missing soldiers whose helicopter crashed off Queensland’s far north coast.

A major search will expand on Monday for crewmen identified as Captain Daniel Lyon, Lieutenant Maxwell Nugent, Warrant Officer Class Two Joseph Laycock and Corporal Alexander Naggs – all members of the 6th Aviation.

They were in a Taipan MRH-90 helicopter taking part in the Talisman Sabre joint-military training exercise with the US and other allies when it crashed on Friday about 10.30pm in the sea near Hamilton Island in the Whitsundays.

Parts of the stricken helicopter were found on Saturday, but the main body of the aircraft is yet to be recovered.

It is the second time an Australian MRH-90 has been involved in an emergency this year after a Taipan ditched into waters off the NSW south coast in March.

Forty-seven MRH-90 helicopters have been grounded until further notice.

Australian Defence Force chief General Angus Campbell would not discuss the immediate future of the MRH-90 helicopters, instead saying the focus remained on the missing men.

“There will be an investigation as there always is in these circumstances and we will look to that to understand what has occurred here,” he said.

Royal Australian Navy sailors scan the horizon near Lindeman Island in the Whitsundays. Photo: AAP

Defence Minister Richard Marles spoke to ADF personnel on Sunday alongside US Secretary of Defence Lloyd Austin.

“This accident makes very real what this exercise means, the dangers that are involved, and the risks that inevitably come with it,” Mr Marles said.

Prime Minister Anthony Albanese thanked all those involved in the search, saying the incident was a stark reminder that there were “no safe or easy days for those who serve in our country’s name”.

“On behalf of our nation, our thoughts and prayers are with the families, friends and colleagues of those who are missing,” he told reporters on Sunday.

Specialist navy divers have joined Queensland police and crews from the HMAS Brisbane, HMAS Adelaide and USS Miguel Keith in their search for the missing Taipan.

An exclusion zone is in place in waters south of Hamilton Island, from the southern tip of Long Island east to Perseverance Island, south to Cole Island and west to the mainland at Round Head.

“We’re focused on bringing them home, supporting their families and getting to the bottom of what happened,” Australian Army chief Simon Stuart said.

Members of the public who find crash material have also been urged to contact investigators.

The joint exercises, mostly being held in regional Queensland, resumed late on Saturday in the Northern Territory and Western Australia after an initial pause.