The driver of a maroon Holden Astra, a 39-year-old woman, and a rear seat passenger, a boy aged about 12, died at the scene.

The occupants of the Astra are understood to be from Queensland.

The car collided with a semitrailer about a kilometre north of the Tindalls Lane overpass, on a new section of the recently opened Princes Highway, about 11.45am.

The front seat passenger of the Astra, a girl aged approximately 14, was treated at the scene by NSW Ambulance paramedics before being airlifted to Sydney Children’s Hospital by the ambulance rescue helicopter, where she remains in a critical condition with serious head injuries and fractures.

The driver of the truck, a 41-year-old man, was treated at the scene by NSW Ambulance paramedics for shock. He was taken to Shellharbour Hospital for mandatory blood and urine testing.

Nowra police Inspector Deborah O'Reilly confirmed the car was travelling south when it collided with the northbound truck. 

Wollongong’s Crash Investigation Unit was working to determine what caused the crash, Insp O’Reilly said. 

“It appears that the truck may have run over the sedan … certainly the sedan has sustained a great degree of damage,” Insp O’Reilly said. 

Crash Investigators will try to determine the exact circumstances surrounding the crash.

Inquiries are continuing.