The only road connection between the West Coast and Otago - cut by a landslide - is likely to remain closed until Friday. Milford Road in Fiordland is also closed.
Work is underway to clear the major slip that closed State Highway 6 south of Diana Falls, between Haast and Makarora, on Wednesday morning.
Transport Agency West Coast area manager Mark Pinner says the slip, which is about 50 metres high and contains 500 tonnes of debris, has stabilised enough to make it safe to start clearing work.
But he says because of the damage done to the road, and the rockfall covering a large culvert, it was not feasible to re-open it on Thursday.
The stability of the rock face above the road was being assessed after the rain eased.
Meanwhile the Transport Agency says the Milford Road is unlikely to reopen on Friday because more bad weather is forecast.