SYDNEY, April 15 (Xinhua) -- A catastrophic grassfire is continuing to threaten life and property in Sydney's southwest on Sunday, with over 500 firefighters desperately trying to contain the blaze as it encroaches on one of Australia's largest army barracks.

While the threat was downgraded Sunday morning, New South Wales State Rural Fire Service Spokesperson Greg Allen told Xinhua that unseasonably hot autumn weather and strong 60 km per hour westerly winds have reignited the blaze that started Saturday, and made it extremely difficult for fire crews to contain.

"There is still a significant risk of embers spreading and starting separate spot fires in the area," he said.

As of midday, residents in the suburbs of Voyager Point, Pleasure Point, Sandy Point, Alfords Point, Menai, and Barden Ridge were urged to seek shelter and warned by authorities that "it is too late to leave."

While it was not clear how many homes and properties have been damaged, the wildfire has at this stage burnt through at least 1,000 hectares of land, crossing creeks, rivers and train lines.

Of most concern is the Holsworthy Army Barracks where stockpiles of fuel, ammunition and explosive materials are stored.

With all non-essential personnel evacuated on Saturday, 15 water-bombing aircraft were deployed to stave off the blaze and protect the base.

Although the facility is no longer under direct threat, Allen said the risk of embers is still very high.

A full investigation will now take place to determine what started the blaze, with police speculating the grassfire may have been "deliberately lit."

Train services to the southwest of Sydney remain closed.