State Highway 1 south of Kaikōura is closed after rocks fell onto a car this afternoon.
The incident occurred immediately south of the Parititahi Tunnel about 4.20pm. Rain has been falling heavily in the area triggering small rockfalls at the site.
The New Zealand Transport Agency (NZTA) said: "A rock the size of two basketballs which fell from a height south of Kaikōura's Parititahi road tunnels landed on and damaged a southbound car late this afternoon.
"The driver and sole occupant of the vehicle was not seriously injured and did not seek medical treatment."
The road was blocked and a detour would add about two hours' travel time. The road will remain closed overnight.
NZTA said geotechnical advisors would inspect the area at first light and the road closure will be updated at 9am Saturday.
Traffic in Kaikōura going south is being detoured onto the Inland Road via Waiau, aiming to keep that route for light vehicles.
Trucks and heavier vehicles going south are being detoured in Marlborough onto the Lewis Pass Alternate Route and from Waipara north onto the Lewis Pass route (State Highway 7).
North of Cheviot, light vehicles can take the Leader Road.