Work to clear avalanche and rockfall debris from the Milford Road was continuing today.
Road access to Milford Sound was cut for a second day yesterday after Tuesday's series of earthquakes and aftershocks.
An avalanche about 1pm on Tuesday swept a 25m-wide wall of boulders, rock andmud across both lanes of the highway near the Divide and Lower Hollyford Road.
The largest boulder - the size of a small car - was removed and one lane opened for traffic leaving Milford Sound, but the route was closed again by a second rockfall on Tuesday night.
Transit advised yesterday that the road would be closed probably until tomorrow to allow slip clearance work.
Transit regional networks operations manager Murray Clarke said staff were also closely monitoring the avalanche risk, which was high at this time of the year, and might have to use controlled explosives to remove the buildup of snow in the "avalanche start zones".
"We'll have a better idea later today on progress and when we'll get the road open," Mr Clark said.
"There's still a number of unknown factors like the weather and getting the slip cleared properly before it's safe to reopen."
Tourism operators in isolated Milford Sound were used to road closures affecting business at this time of year, but snow was usually to blame, not earthquakes, Milford Sound Development Authority operations manager Dave Inwood said.
"We do have these `lock-ins' and they're more frequent in September and October than during the winter itself," Mr Inwood said.
"It's all part of the tourism business here. We're at the mercy of the road crews."
However, Mr Inwood said it was a "beautiful day" in Fiordland today and tourist flights were getting in and out.
Destination Fiordland manager Lisa Sadler said people with plans to visit Milford Sound were being offered a range of alternative activities and tours.
"A lot of people are being diverted across to Doubtful Sound, which is arguably just as beautiful," she said.
