Update 6pm:
Around 90 firefighters have worked to slow the spread of a fire near Waterfall today.
NSW RFS said a backburn is planned for this tonight which will bring fire activity closer to Waterfall and the Waterfall train station.
Crews will remain on the ground throughout the night.
Commuters and residents as far away as Campbelltown, and Helensburgh may notice smoke.
People with asthma or a lung condition are being advised to reduce outdoor activities.
Some trails in the Royal National Park are closed, including the Uloola Falls track, the Couranga walking track and the Forest Path walking track.
People are advised to avoid the area.
Update 11am:
The fire has crossed the Couranga Track and is heading north towards the Uloola Fire Trail.
Aircraft are water bombing the fire to help bring it under control.
Smoke is visible in the area and people are reminded to only report unattended fires to triple-0.
Tuesday 9am:
Around 80 firefighters are working to contain a bush fire in the Royal National Park.
The blaze broke out near McKell Avenue on Monday afternoon, around 2.5km south east of the Waterfall township.
Despite cooling conditions overnight the fire has continued to grow. It is currently covering around 46 hectares.
Ground crews from NSW RFS and National Parks and Wildlife Service are being supported by helicopters to keep the fire within identified containment lines of the Couranga Track.
There are currently no threats to property.
McKell Avenue remains closed between Waterfall and the Joan Holland Bridge at Sir Bertram Stevens Drive.
Monday 4pm:
Rural firefighters are responding to a bush fire at Waterfall.
Sutherland Shire Rural Fire Service crews were called to McKell Avenue just after 3pm after reports of an out of control fire.
The RFS website currently lists the fire as advice under the alert levels.
Advice means that there is no immediate danger.
Thor, the large air tanker, is on its way to assist firefighters on the ground bring the fire under control.
McKell Avenue is closed from Waterfall Station to Lady Wakehurst Drive.
People are advised to avoid the area.
Helensburgh Rural Fire Brigade have advised there is no fire at the Ridge. The reported fire was smoke from the Waterfall blaze.
Information on the fire will be updated at www.rfs.nsw.gov.au.
