Police are appealing for witnesses following a truck crash which has killed one man and injured another near Iluka.

About 12.40am two semi-trailers were travelling in opposite directions along the Pacific Highway, about two kilometres north of the Iluka Road turn-off.

Initial inquiries suggest one of the vehicles might have crossed onto the incorrect side of the roadway and collided with the oncoming truck.

Police from Coffs/Clarence and Richmond Local Area Command attended the scene, along with Crash Investigators from Ballina, NSW Fire Brigades and Ambulance paramedics.

The driver of the southbound truck, which was carrying wrecked cars — some of which were thrown onto the roadway as a result of the impact — was airlifted by Westpac Rescue Helicopter to Lismore Hospital. His condition is unknown.

The driver of the north-bound truck, which was carrying chemicals, died at the scene of the incident.

Investigations into the cause of the crash are continuing this morning. It remains unclear which vehicle crossed onto the incorrect side of the road.

The Pacific Highway remains closed to traffic as police carry out their investigations.

Motorists are advised to detour via Summerland Way from Grafton, through Casino and Lismore, and via the Bruxner Highway in the north.

B-double drivers are advised they can not travel between Woodburn and Casino and must exit the Pacific Highway at a different point.

For more details on traffic arrangements, please refer to the RTA website.