Manawatu Gorge will remain closed for the rest of the day after a number of rockfalls early this morning.
The gorge, which is frequently affected by slips, was closed to traffic just after 4am today.
The New Zealand Transport Agency says the route will be reassessed at 5pm.
Alternative routes are via Saddle Rd or Pahiatua track.
Police are warning drivers to take care.
Today's closure is the latest in at least two nature-related closures this year, with another rock slip in April and flooding closing the road in June.
A truck carrying animal blood which left the road and teetered over the edge also reduced the highway to one lane last week, then closed it briefly while a crane removed the vehicle.