There"s no longer any hope of locating survivors from a military helicopter crash, Australia"s defense minister says. A significant amount of wreckage was recovered, pointing to a "catastrophic incident", Richard Marles told reporters on Monday. The crash happened during a multinational military exercise off Lindeman Island on Friday night. Australian authorities have launched a full investigation. Australia"s army chief had grounded a fleet of military helicopters after the crash, which left four crew members missing, and now feared dead. Lt Gen Simon Stuart said none of the army"s 45 MRH-90 Taipan helicopters - the craft involved in the accident - would be flown again until they were found to be safe. Australia has previously grounded its Taipans for safety reasons. "We are not flying the MRH-90 today and won"t until we think it is safe to do so," Gen Stuart told reporters in Sydney on Sunday. Friday"s crash happened at about 22:30 local time (12:30 GMT) over the Whitsundays, a group of islands off the coast of Queensland. The missing soldiers onboard the aircraft were identified by the army as Capt Danniel Lyon, Lt Maxwell Nugent, Warrant Officer Class Two Joseph Laycock and Cpl Alexander Naggs. All of them belonged to the Sixth Aviation Regiment, based in Sydney. The helicopter went down during drills as part of Exercise Talisman Sabre, the massive training exercise which gathers 30,000 military personnel from Australia, the United States, and several other nations. Canberra had announced before the crash that it would be replacing its ageing European-made Taipan helicopters with US-made Black Hawks. Officials had complained about having to repeatedly ground the fleet for maintenance and safety issues. As recently as March, the fleet was pulled from the skies after an engine failure in one of the helicopters during a training exercise, forcing the crew to ditch into the sea off the coast of New South Wales. There were no casualties in the March training exercise. The other MRH-90s were returned to operations on 6 April with "risk mitigations". Gen Stuart said the current aim was to keep the Taipans in service until 2024 but "what happens between now and then, from what we learn from this incident, is yet to be determined". Australian Prime Minister Anthony Albanese described the recent crash as a stark reminder "that there are no safe or easy days for those who serve in our country"s name". US Defence Secretary Lloyd Austin, speaking in the northern city of Townsville, said the US would provide any assistance it could. — BBC