The NZ Transport Agency says it will be midday tomorrow at the earliest before the rockfall is cleared and the highway opened again.
The road also remains closed further west on the highway, at the Diana Falls slip site near Haast Pass.
Recent heavy rain is believed to have caused the 2000cu m fall which occurred at 6am today about 15km south of Makarora, Transport Agency Senior Network Manager John Jarvis said
The slip is roughly 50 metres long and 4-6 metres deep.
''We currently have a helicopter using a monsoon bucket to sluice away any remaining loose rock from the top of the rock fall site,'' Mr Jarvis said.
''This rockfall is larger than one two years ago about 100 metres further north. The speed of the clearing work will depend on the size of some rocks with indications that there are some very large slabs of rock buried in the debris.''
''We understand our customers will be inconvenienced by this situation and are making every effort to get at least one lane of the highway open as soon as it is safe to do so. ''
Mr Jarvis said there was enough equipment and personnel on site to begin removing debris as soon as they received the all clear.
For the latest on road conditions including this rock fall freephone 0800 4 HIGHWAYS or go to www.highwayinfo.govt.nz
