SYDNEY—Three American firefighters were killed after their air-tanker crashed while battling wildfires ravaging southeastern Australia.

The plane, a C-130 Hercules, crashed in the state of New South Wales some 200 miles southwest of Sydney about 1:30 p.m. on Thursday, said Shane Fitzsimmons, commissioner of the NSW Rural Fire Service. He said there was a large fireball after the plane hit the ground heavily and there were no survivors.

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