The furious mayor of an area worst hit by Australia's bushfire emergency is demanding answers after the military was blamed for starting a huge blaze, as cooler conditions Thursday aided fire crews.

Thousands of largely volunteer firefighters have been battling infernos for more than a week across the state of New South Wales that have destroyed more than 200 homes, with the Blue Mountains region west of Sydney the focal point.

Cooler weather was helping Thursday, with several major blazes downgraded, although authorities urged communities not to be complacent with 66 fires still alight, 24 of them uncontained and winds still a concern.

One of the biggest and fiercest infernos still blazing -- which has a perimeter of more than 300 kilometres (186 miles) and has ripped through 47,000 hectares (116,000 acres) of land -- was started by the military, a fire service investigation found.

The huge blaze, near Lithgow, was a major worry this week with authorities on Tuesday deciding to deliberately merge it through backburning with another nearby fire at Mount Victoria to preempt a deterioration in conditions.

NSW Rural Fire Service chief Shane Fitzsimmons said an official investigation found it was started by exploding ordnance on a live firing range on Wednesday last week.

"It wasn't deliberate, it was a side-effect of a routine activity ... and clearly there was no intention to see fire start up and run as a result of that activity," he said, adding that the military had fully cooperated.

The defence department is yet to comment on the findings, but Blue Mountains mayor Mark Greenhill was furious.

"I would have thought the community of the Blue Mountains is owed something," he told the ABC television, adding that residents lived in fear for a week.

"I would have hoped on a day like that which was a dry day, a hot day, with the winds -- the Australian military would have known it wasn't a good time to be igniting.

"The fire has caused great concern to my community, it's done damage to my community and it just shouldn't have happened."

So far, more than 124,000 hectares (306,000 acres) of land has been burnt across NSW in its worst bushfire emergency in nearly 50 years.

After dire warnings that extreme heat and strong winds would cause chaos on Wednesday, the high-risk strategies of aggressive backburning, building containment lines and strategic planning averted what had been feared to be a major disaster.

"There is no immediate threat across any of our fire grounds to people at this stage, but because they're (the major fires) all at 'watch and act', that signals that circumstances could change," said Fitzsimmons.

While homes have been destroyed, only one person has died as residents heeded advice either to flee or head to evacuation centres.

Source: AFP