Up to 100 trucks will be needed to clear a rockslide on the eastern side of Haast Pass that has kept State Highway 6 closed since early this morning.

Transport Agency West Coast area manager Mark Pinner said rocks as big as houses would need to be broken up before they could be moved.

The slip came down about 2am at Izzy's Bluff, between Makarora and Hawea.

Rocks had fallen across the highway and were continuing to fall late this morning. Contractors were working to break up and remove an estimated 1000 cubic metres of rock.

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They would then stabilise the slip to prevent more loose material falling down.

Transport Agency Central Otago area manager John Jarvis said geotech engineers were brought in from Alexandra to assess the situation.

An update on the road status was expected this afternoon.

- The Greymouth Star