Emergency services have now said the accident is a four-car, nose to tail crash with four people involved.

Two patients, believed to be in their 50s and from separate cars, are being transported to hospital.

Traffic on the Princes Motorway - not the highway as reported earlier by Live Traffic NSW - is reportedly very slow moving and backed up to Five Islands Road, so peak-hour motorists are advised to allow extra time.

Earlier

One southbound lane of the Princes Highway is closed at Kembla Grange after a two car accident near Northcliffe Drive at about 5.45pm.

Emergency services are attending and drivers are advised to allow extra time.

More to come.