Three Americans were killed after their C-130 plane crashed during a firefighting mission in Australia.

The crash took place on Thursday afternoon (Australia time). Pending next-of-kin notification, the names of the three firefighters have not been released.

According to the Australian Civil Aviation Safety Authority, the mission of the C-130 was to drop fire retardant in a valley in an attempt to slow down a fire front. A C-130 modified for firefighting duties can carry approximately 15,000 liters of water or fire-retardant liquid.

“Tragically, there appear to be no survivors as a result of the crash down in the Snowy Monaro area,” said Shane Fitzsimmons, the chief of rural fire services for the southeastern state of New South Wales. “[The plane] impacted heavily with the ground and initial reports are that there was a large fireball associated with the impact of the plane as it hit the ground. There is no indication at this stage of what caused the accident.”