Investigations are ongoing following a serious traffic incident which occurred over the weekend.

Around 11:45am on Sunday, January 21, emergency services were called to the Gwydir Highway at Eatonsville, about 20km west of Grafton, following reports a car had collided with a parked B double truck.

Officers attached to the Coffs/Clarence Police District attended the scene and found the 55-year-old female driver and 52-year-old female front seat passenger suffering serious injuries.

They were treated by NSW Ambulance paramedics, and the driver was later flown to Lismore Base Hospital with a fractured collarbone and other injuries.

The 52-year-old female passenger was flown to the Gold Coast University Hospital with serious leg and internal injuries.

A 63-year-old man and a 16-year-old boy, who were in the backseat, were taken to Coffs Harbour Hospital with minor injuries.

The truck was unoccupied.

A crime scene was established, with investigations ongoing.

Anyone with information is urged to contact Coffs Harbour Police or CrimeStoppers on 1800 333 000.