Australian firefighters got some respite Friday from the hot, dry weather that has been fuelling wildfires, but the break may have come too late for thousands of the country's best-known animals, a government agency said.

Swiftly spreading forest fires in New South Wales have reduced 400,000 hectares of bush to ashes since they began Christmas Eve. Thousands of people have been forced to evacuate. But wildlife experts say Australia's national icon, the koala, is far too slow to escape the fires.

A spokesperson for the National Parks and Wildlife Service said it's likely that thousands of koalas have already died or been injured in the outbreaks and, since vast tracts of their natural habitat have been destroyed, the future of thousands of others is uncertain.

The number of koalas in Australia had already dipped below 100,000, the service's director said. And it could take 15 years for some local koala populations to recover from the fires' devastation.

In Sydney, fire officials welcomed a sudden drop in the searing temperatures of recent days, but they said it could still be more than a week before all 100 of the fires are brought under control because erratic winds are making their paths unpredictable.

Officials believe about half of the fires were set deliberately by youths. On Friday, two more teenaged arson suspects were arrested. Twenty-three young people, including a nine-year-old, have now been arrested on suspicion of starting the fires.