The Transport Agency says damage beneath the Manawatu Gorge slip could delay its re-opening, which is scheduled for mid year.
State Highway Three has been closed since August, when a slip brought down more than 300,000 cubic metres of hillside. Several more have ocurred since then.
Contractors are working round the clock to clear the route, which links Manawatu and Hawke's Bay.
The agency estimates 120,000 cubic metres of material is still to be moved.
Until the bridges under the slip are uncovered and assessed, NZTA says it won't know exactly when the road can re-open.