One person died in a mid-morning crash between two trucks on the busy State Highway 65 near Springs Junction.
A second person, aged in his 20s, was flown by the NZCC West Coast Rescue Helicopter to Grey Base Hospital with moderate injuries.
The crash occurred about 9km north of Springs Junction township, on the Shenandoah highway, where truck numbers have skyrocketed since it became the main highway between Christchurch and the Picton ferries with the closure of the coastal route after the Kaikoura earthquake.
Diversions were in place after the crash, and the New Zealand Transport Agency advised motorists to take the alternative route through Reefton.
The crash closed the highway about 500m south of the intersection with West Bank Rd.
A spokesman at the Springs Junction garage said at one stage about 30 cars were backed up and some trucks.
However, the trucks were going over the Rahu Saddle to Reefton, and the backlog had cleared by 11am.
The New Zealand Transport Agency said the detour route for south-bound traffic was State Highway 6 from Murchison then State Highway 69 to Reefton, and on to State Highway 7 to Springs Junction, and the reverse for north-bound traffic.
Journey manager Lee Wright said the detour was a long a very winding stretch of the Buller Gorge so "extreme caution is needed for all vehicles".
- Greymouth Star