Firefighters remain on high alert around a huge bushfire believed to be deliberately lit in southwest Sydney with winds predicted to pick up later in the day.
Exhausted firefighters are facing another "challenging and difficult" day battling a bushfire, believed to have been deliberately lit, that is still burning out of control south of Sydney.
The fire, which started at about 2.30pm on Saturday, has blackened more than 2400 hectares and continues to burn towards Barden Ridge.
More than 500 firefighters faced walls of fire, fanned by 70 km/h wind gusts on the city's southern fringe on Sunday and through the night.
"It is still an active fire ground but we are not seeing the sort of weather extremes, particularly with the wind that we saw yesterday," Rural Fire Service Commissioner Shane Fitzsimmons told reporters in Sydney on Monday.
Heathcote Road remains closed on Monday in both directions from Lucas Heights to Holsworthy.
About 250 firefighters are still working to halt the fire while a fleet of 15 aircraft will water-bomb the "dynamic" firefront, Mr Fitzsimmons said.
Fire chiefs have ordered crews to backburn in an effort to contain the blaze while simultaneously stopping the fire from advancing toward properties.
Westerly winds are expected to pick up again on Monday afternoon but will not be as extreme as conditions at the weekend.
"It's certainly not the reprieve we're looking for," Mr Fitzsimmons said.
"It's still going to be challenging, it's still going to be difficult."
A strike force has been established to investigate the blaze which is believed to have started in Wattle Grove.
So far no homes have been lost though there has been some property damage, Mr Fitzsimmons said.
He said it was "extraordinary" that the only reported losses had been fences, cubby houses and garden sheds.
"I am not being dismissive of the loss in any way, but the fact is that's the loss we are talking about rather than people's homes being badly damaged or destroyed," he said.
"It's quite significant."
The RFS cautioned that while the threat had eased, residents in the areas of Voyager Point, Pleasure Point, Sandy Point, Alfords Point, Barden Ridge, Illawong, Menai and Bangor should continue to monitor the situation and be
prepared to activate bushfire survival plans should conditions change.
"We have had reports of impact on properties in west Menai and Barden Ridge but our crews at the moment are solely focused on fighting the fire," he told AAP.
The blaze was downgraded from watch-and-act to advice about 2am on Monday.
Police are expected to address media about their investigations into the blaze's origin later on Monday.