Heathcote bushfire: Crews battle Royal National Park blaze

The fire is burning in the Royal National Park on the eastern side of the Princes Highway, south of Heathcote.

It is understood the blaze started after a spot fire broke containment lines of a controlled hazard reduction burn at about 1pm.

The spot fire quickly got out of control and turned into a 200 hectare blaze, with firefighters calling in a waterbombing aircraft on Saturday afternoon to help contain the blaze.

Conditions have now eased and crews have managed to get the fire back under control.

The fire caused major delays on the Princes Highway, with traffic backed up in both directions for hours.

Parts of the highway and surrounding roads were closed intermittently throughout the afternoon, with motorists urged to delay their trip or use an alternate route.

Train services in the area were also temporarily suspended, with buses replacing trains on the T4 Eastern Suburbs line and Illawarra and south coast line between Sutherland and Waterfall.

The blaze is now burning in a north easterly direction, with crews continuing to work overnight.

There is currently no threat to properties in the area and the Princes Highway is open in both directions.

Originally published as Crews to battle huge bushfire overnight