A major slip has closed State Highway 6 at Chelsea Creek.
The slip included toppled trees and blocked both lanes of the Haast Highway.
Haast police and Transit staff said the road would be closed for several hours because it would take some time to get a grader to the scene.
They were focused on getting one lane open but motorists were being urged to turn back at both ends of the State Highway at Makaroa north of Lake Hawea and at Haast on the West Coast.
There is no alternative route to or from the coast on State Highway 6.