All 23 US marines on board a military aircraft that crashed in northern Australia have been accounted for, police said Monday, as investigators worked to uncover the cause of an accident that left three dead and five seriously injured. The Boeing MV-22B Osprey tilt-rotor aircraft crashed on Melville Island, north of Darwin, on Sunday morning during a routine military exercise for locally based troops. Authorities confirmed to AFP that the 15 marines who were not dead or seriously injured had now been accounted for. They either suffered minor injuries or were unhurt. Authorities have launched investigations into what caused the crash. Air traffic control broadcasts from Darwin airport included communications from the crash site describing dark smoke and a “significant fire”. Northern Territory Police Commissioner Michael Murphy told local media that emergency responders had been helped in their initial efforts by the location of a nearby airstrip. “We were quite fortunate having that airstrip close by to the crash site… the ability to land in close proximity to the crash site and the speed of the assistance resulted in some casualties being treated more quickly and probably saved some lives,” he said. Murphy described the site as being “heavy bushland”, adding that some rescuers came by air and some were able to use a four-wheel drive, although it was “a long process, probably a lot of walking as well”. “It was just a really big effort from everyone that attended there and coordinated the rescue response just to care for those who were injured,” he said. Northern Australia has become an important staging ground for the US military in recent years, as Washington and Canberra work together to counter China’s growing clout in the Asia-Pacific region. Australian defence minister Richard Marles told public broadcaster ABC on Monday morning that the loss of life would be felt by US and Australian forces. “These are very tight-knit communities,” he said. US Defence Secretary Lloyd Austin praised the fallen Marines, who he said “served our country with courage and pride, and my thoughts and prayers are with their families today, with the other troops who were injured in the crash, and with the entire (US Marine Corps) family”. The Osprey aircraft has a troubled history, blighted by a string of fatal crashes over the years. The tilt-rotor aircraft can land and take off like a plane, or vertically like a helicopter.