Multiple investigations are underway following an aircraft crash which killed three US marines on Melville Island, north of Darwin, on Sunday.
Another five marines remain in hospital after the MV-22B Osprey crashed on the Tiwi Islands around 9.30am (local time) during a military exercise.
Australian Defence Minister Richard Marles said the crash had triggered "a number of investigations".
"That process is already underway," he told ABC Radio Darwin.
"We will work closely with the US around the jurisdictional basis and the interaction of those investigations".
A St John Ambulance spokesperson said the service had helped CareFlight and the Australian Defence Force move 20 patients from various locations in Darwin to the Royal Darwin Hospital (RDH) on Sunday.
They said seven patients had been transported to RDH in St John vehicles, with one in a critical condition and six in a serious condition.
Marles said out of the five marines who remain in hospital, one was in a critical condition.
He said local services were on the scene of the crash near Pickertaramoor, two kilometres inland on Melville Island, "almost immediately".
"I think that's played a really important part in making sure we've had as many people survive as possible from this crash," he said.
"Twenty-three people were on board and 20 people have survived the crash, which is remarkable."
He said the US government would be responsible for publicly identifying the marines who had died.
"We now will work closely with the US government around repatriation of their remains," he said.
Osprey a 'unique' aircraft
This is the sixth fatal crash involving a Marine Osprey since 2012, resulting in a total of 19 deaths.
However, Marles refused to say that Australian defence personnel would be prevented from boarding the aircraft while the investigation is underway.
"The Ospreys have remarkable capability," he said.
"We routinely work with the US with the Osprey.
"We need to let this investigation play out to understand exactly what has happened here."
Keith Tonkin, who served 15 years in the Royal Australian Air Force, followed by nearly a decade of experience in international and domestic airline operations, said the Osprey was a very specific aircraft type.
"This aircraft can take off vertically and fly relatively fast and carry more than a helicopter can carry on that sort of mission," he told News Breakfast.
"It was designed for a very specific task and that was to fly to places where we don't have a prepared runway or helicopter landing site.
"Even if it's an open area, it can land and take off and carry quite a few people and because of that, we have a higher number of fatalities if the aircraft is fully loaded.
"We can only imagine that something horrible happened to cause that, knowing that the people operating the aircraft [are] highly skilled and experienced."
Military analyst and retired US Air Force Colonel, Cedric Leighton, said the investigation would consider mechanical and maintenance issues with the aircraft.
"There have been accidents throughout its history. And of course its unique characteristics, which are kind of a cross between a helicopter and a fixed wing aircraft, make it perhaps more vulnerable to mechanical issues than other aircraft," he said.
Rescue turns to recovery
NT Police Commissioner Michael Murphy said all injured marines who had been onboard the chopper had been taken back to the mainland.
"As operations continue throughout today, we've moved from a rescue mission to a recovery mission," he said.
The commissioner said the response had been "complex" due to the remote location and rough terrain, and praised the efforts of all emergency services that responded.
"The crashed Osprey was in heavy bushland. The clinic staff, our police … were deployed to the location, [and] helicopters [and] a number of aircraft were immediately dispatched through defence, and other civilian services and CareFlight," he said.
"The ability to land in sort of close proximity to the crash site, and the speed of the assistance, ended in some casualties being treated quicker and probably saving lives."
He said the NT emergency operations centre was still actively involved in the crash response.
"There's still a continuing operation underway," he said. "This is going to be going on for a few days."
This story was originally published by ABC.