Hawke's Bay's State Highway 50 is down to one lane due to a slip, south of Maraekakaho.
Motorists were advised to take care in the area, and the speed limit has been reduced to 30kmh.
A police spokesperson said they were advised of the slip just before 11.40am.
It was covering the southbound lane, and contractors had been called to clear it.
They were unable to confirm what time the road would be fully cleared.