A forecast of heavy rain has delayed the reopening of the road to Milford Sound, closed since boulders weighing as much as 500 tonnes fell on the road during a storm on Friday night.
The New Zealand Transport Agency (NZTA) had hoped to clear enough debris to reopen a single lane of the road tomorrow.
But NZTA area manager Peter Robinson says that while more than half the slip has been cleared, the rain that is forecast and the time it would take to ensure one lane was safe and secure, meant it was safer to re-open the popular tourist road on Thursday.
Mr Robinson said earlier forecasts of boulders up to 200 tonnes were conservative.
"The slip had covered about 200m of road and included rock as large as 500 tonnes."
Contractors have drilled holes in the large boulders and then detonated explosives so the rocks could be broken up enough to carry them away.
The only road into the popular tourist destination is plagued by slips and avalanches during the winter months.
About 450,000 people a year visit Milford Sound and two development projects, on a mono-rail and a tunnel, have been proposed to improve access to the beauty spot. Te Anau, the closest town, is 119km away.
NZN