Emergency rescue and recovery personnel said late on Saturday debris consistent with a helicopter part had been found near the crash site but could not confirm if it was from the missing aircraft.
The MRH-90 Taipan helicopter went down about 10.30pm on Friday.
A large-scale search is under way to find the crew and their families have been notified.
Talisman Sabre Exercise Director Brigadier Damian Hill told reporters on Saturday afternoon the missing crew came from the 6th Aviation Richmond Unit, based at the Holsworthy Army barracks in Sydney.
He said his thoughts were with their families and anyone impacted by the accident.
"For those service members, those veterans, and those members of the community that are suffering as a consequence of this ... I ask that you reach out to the relevant support networks," he said.
He said he had paused the exercises to allow personnel to contact family.
"I wanted people to contact their families to let them know they were safe and what was happening," he said.
The aircraft was involved in Exercise Talisman Sabre, a training operation that involves defence forces from Australia, the United States and other allies.
The joint exercises, mostly taking place in regional Queensland, resumed late on Saturday in the Northern Territory and Western Australia.
The entire fleet of Australia's MRH-90 Taipan helicopters has now been grounded as a precaution.
Queensland Police Acting Assistant Commissioner Douglas McDonald confirmed debris had been recovered.
"At this time we have located a number of items of debris that would appear to be from the missing helicopter," he said.
He asked anyone who finds anything on the beaches around Hamilton Island to contact police.
"Can I encourage if any members of the community are on those beaches and come across anything that they might think is debris related to this particular incident, if they can contact police immediately and don't touch the items," he said.
Brig Hill said specialist divers would be brought in and sonar used from Sunday to find the aircraft, thought to be in deep water.
Defence Minister Richard Marles said the missing helicopter was taking part in a mission that involved a second chopper, which immediately started a search and rescue operation.
"Defence exercises which are so necessary for the readiness of our defence force are serious," he told reporters in Brisbane on Saturday.
"They carry risk.
"As we desperately hope for better news during the course of this day we are reminded about the gravity of the act which comes with wearing our nation's uniform."
Chief of the Defence Force General Angus Campbell said Queensland authorities, members of the public and US personnel were taking part in the search.
"Our focus at the moment is finding our people and supporting their families and the rest of our team," he said.
"This is indeed a terrible moment."
US Defence Secretary Lloyd Austin offered his support while speaking at high-level strategic talks in Brisbane.
"It's always tough when you have accidents in training," he said.
"The reason why we train to such high standards is so that we can be successful - we can protect lives when we are called to answer any kind of crisis."
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.
The Taipan helicopter has earned a reputation as unreliable in recent years, with malfunctions and technical issues forcing several groundings of Australia's fleet.
