BRISBANE, Australia >> Four air crew members were missing after an Australian army helicopter ditched into waters off the Queensland state coast during joint military exercises with the United States, officials said Saturday.

The MRH-90 Taipan helicopter went down near Hamilton Island, a Great Barrier Reef tourist resort, at about 10:30 p.m. Friday, Defense Minister Richard Marles said.

A search was underway to find the crew, and their families had been notified, officials said.

A rescue helicopter reported spotting debris Saturday morning near Dent Island in the Whitsunday Islands group.

The Taipan was taking part in Talisman Sabre, a biennial joint U.S.-Australian military exercise that is largely based in Queensland. This year’s exercise involves 13 nations and more than 30,000 military personnel.

Marles said the helicopter ditched, which refers to an emergency landing on water. He said it was taking part in a mission that involved a second helicopter, which immediately started a search and rescue operation.

“Defense exercises, which are so necessary for the readiness of our defense force, are serious. They carry risk,” Marles told reporters in Brisbane. “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.”

Defense Force Chief Gen. Angus Campbell said Queensland state authorities, members of the public and U.S. military 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, ” Campbell said. “This is indeed a terrible moment.”

It is the second emergency involving an Australian Taipan this year, after one ditched into the sea off the New South Wales state coast in March. That helicopter was taking part in a nighttime counterterrorism training exercise when it ran into trouble. All 10 passengers and crew members were rescued.

U.S. Defense Secretary Lloyd Austin was in Brisbane for a meeting on Saturday and is due to travel with Marles to north Queensland on Sunday to see the exercise.

The exercise has been paused by the search.

Austin and U.S. Secretary of State Antony Blinken paid tribute to the missing air crew at the outset of a meeting with their Australian counterparts, Marles and Foreign Minister Penny Wong.

“It’s always tough when you have accidents in training, but … the reason that we train to such high standards is so that we can be successful and we can protect lives when we are called to answer any kind of crisis,” Austin said.

“Our guys tend to make this look easy and they make it look easy because they’re so well exercised and rehearsed and trained, and this is unfortunately a part of that, what it takes to get them to where we need them to be,” Austin added.

Blinken said, “We’re so grateful to them for their dedication, for their service, for everything they’ve been doing to stand up for the freedom that we share and that is what unites us more than anything else.”