State Highway 6 on the West Coast is expected to remain closed until at least midday tomorrow, after a large piece of the cliff wall fell on the road.
The boulder is blocking the road near Barrytown in the Grey District - the main road between Punakaiki to Greymouth
Police said the rock will likely keep the road closed until midday, but Waka Kotahi said the road was now closed for the weekend and the next update will be on Monday afternoon.
Police are advising motorists to use an alternative route.