SYDNEY — Three firefighters from the United States were killed Thursday as a large aircraft being used to battle bushfires crashed south of the Australian capital, Canberra, the Rural Fire Service in New South Wales said.

The cause of the disaster was not immediately known. The plane went down Thursday afternoon as blazes were threatening parts of New South Wales, ending a brief lull in the country’s summer of disastrous wildfires.

The plane was a C-130 Hercules operated by Coulson Aviation, a Canadian company that helped battle last year’s California fires. The aircraft crashed in the Snowy Mountains of New South Wales, about 70 miles south of Canberra, according to the Rural Fire Service.

Fires were approaching the suburbs of the capital, forcing the closing of its airport to flights. As temperatures climbed and winds picked up, residents in the affected areas around Canberra were told that driving could be deadly and that they should seek immediate shelter.

Australia's wildfires

Rain in recent days — a torrent in some areas, a few drops in others — had offered a small reprieve. But on Thursday, with temperatures soaring over 100 degrees in previously fire-stricken states like New South Wales, fire officials once again issued emergency warnings.

By midday, more than 80 fires were burning, some out of control, in the state’s south, including the Snowy Mountains, the Rural Fire Service said. “We’re in for a long afternoon and night,” it said.

In other parts of the country, which has been gripped by drought and has just ended its hottest and driest year on record, dust storms covered towns.