Cool weather helps in fight against wildfires

Cool weather today allowed 15,000 firefighters to contain many of the wildfires that have been burning out of control across Australia’s most populous state.

For more than a week, about 100 fires - almost half of them deliberately lit - have destroyed 150 homes and razed hundreds of thousands of hectares (acres) of forest and farmland.

No deaths have been reported, but more than 4,400 people have been evacuated.

Even as temperatures dropped, officials refused to say the crisis was over.

Temperatures today were well below the 38C (100 F) forecast, but meteorologists and local officials warned that scorching weather could return and stoke fires in forests that remain tinder-dry.

‘‘We’re not optimistic about the weather in the next 72 hours,’’ New South Wales state fire chief Phil Koperberg said.

Fires continued to burn north, west and south of the nation’s largest city today, and views of Sydney’s opera house and bridge were shrouded in grey smoke.

Residents concerned about the acrid haze flooded emergency services telephone lines.

Smoke swirled through downtown streets and was trapped inside shopping malls and office buildings, setting off dozens of fire alarms.

With visibility poor, some jetliners were diverted from Sydney Airport and dozens of flights were delayed, although the airport continued to operate.

Six people have been arrested for allegedly starting fires. Other arsonists remain at large, police said.

Today, suspected arsonists started five blazes south of Sydney. New South Wales Premier Bob Carr called their actions ‘‘wickedness.’’

The most dangerous fires were along the city’s southwest boundary and in the Blue Mountains national park, 80 kms west of Sydney.

Firefighters there said visibility today was less than 100 metres, hampering efforts to locate fires in the region’s heavily forested and rugged terrain.

National parks were closed across the state. Wildlife officials estimated that thousands of animals have died or have been injured.

‘‘Larger mammals, such as wallabies, kangaroos and koalas, are most at risk because they cannot move fast enough to escape fire,’’ said Julie Barnes, a veterinarian at Sydney’s Taronga Park Zoo.

Jill Dark of the Wildlife Information and Rescue Service said many possums and wallabies had been rescued by volunteers and residents.

‘‘It’s very distressing for people who find a little opossum with all its little whiskers burned off and its paws burned,’’ she said.

Nearly 80% of the 16,000-hectare (40,000-acre) Royal National Park in Sydney’s south has been blackened. It is the world’s second-oldest national park after Yellowstone.

Wildlife officials said the park would need at least 10 years to retain its existing plant and animal life and fully recover.

Australia’s forests are dominated by eucalyptus and other oil-based trees that burn easily but regenerate quickly after fires.