State Highway 6 from Haast township to Makarora has re-opened after it was closed by a slip at Clarke Bluff 10km north of the Gates of Haast on Wednesday.
Up to 300 cubic metres of rock and material fell on to the highway just before 4pm, closing the road to all traffic.
The New Zealand Transport Agency said on Thursday the slip has been cleared, but some debris still remains on the highway, reducing traffic to single lane.
There were a number of smaller slips overnight, including one at Orman Falls, about halfway between Haast township and Haast Pass and contractors are working clearing away any remaining debris.
Motorists are advised to take extra care travelling through the area and to drive to the conditions.