State Highway 6 is closed after a truck crash north of Murchison, which has injured one.
A Waka Kotahi spokesperson says the truck rollover was reported shortly after 1pm on Tuesday.
The highway has been closed in both directions at Rait Road and east of Two Mile Bridge to allow emergency services and contractors to attend and investigate the crash near Owen Junction.
"The closure is expected to last for some time, and there is no estimate for when the highway will reopen," the spokesperson says.
St John responded a first response vehicle along with a manager, a rapid response vehicle and the rescue helicopter.
"We assessed and treated one patient who is being airlifted to Nelson hospital in a moderate condition," the spokesperson says.
Police and the Serious Crash Unit are also on the scene.
There are no local detours, so people travelling between Nelson and Murchison and the West Coast should avoid the area, use an alternative route, or delay their travel until the highway is reopened.
The highway reopened on Tuesday evening.
