The highway was blocked for more than four hours after the collision, which happened about 12.20pm at Stoney Creek, about 7km south of Kew.

Police at the scene, some 45 minutes’ drive from Port Macquarie, said the crash occurred after a south-bound vehicle crossed to the wrong side of the road and into the path of a north-bound van.

The drivers of both vehicles died.

Three people were flown by Westpac Rescue Helicopter to Newcastle’s John Hunter Hospital, while a fourth injured passenger, believed to be a child, was taken by ambulance to Port Macquarie Base Hospital.

Those flown to Newcastle were a woman, 57, who had leg fractures; and a girl, 12, and boy, 11, who had abdominal injuries.

The collision took place on a stretch of highway where work is under way to expand it to dual carriageway.

The road there is a single lane each way and on a gentle curve. There are double white lines between the lanes.

South-bound traffic backed up for 10km; north-bound queues also stretched for kilometres.

Roadworks restricted the scope for detours around the accident scene.

Rescue workers took several hours to free the dead and injured from the badly damaged vehicles, one of which was virtually unidentifiable.

Crash investigations and salvage operations further prolonged the traffic standstill.

The Pacific Hwy was finally re-opened about 4.40pm.