Popular South Island tourist destination Milford Sound will be closed to traffic for at least three more days while workers clear massive boulders which blocked off its only access road in a landslide on Friday afternoon.

NZTA Southland Area manager Peter Robinson said today it would take a minimum of three days to open up the road to a single lane.

Workmen were now building a rock bunt – or retaining wall – so crewmen could work safely in the area, he said.

Some of the boulders were as large as 200 tonnes, with the boulders and other debris covering at least 200m of the road, on the Milford side of Falls creek.

The length of the closure depended on how long it would take to break up the large rocks and remove them.

It appeared the road seal under the rocks had been damaged, Robinson said.

Another four avalanches and two gravel slips on the west and east sides of the Homer Tunnel had struck at about the same time as the landslide that closed the road,  Robinson added.

While a landslide that closed Milford Road two years ago was a larger in volume, the Friday slide had brought down bigger rocks, making it more difficult to clear the road.

Robinson said the single lane would open for all incoming and outgoing traffic to Milford, but emphasised that getting the road clear within three days was optomistic, considering the damage done.

"You have to remember these rocks have had about a 900-metre vertical drop, and they haven’t broken."

Guests and staff still stranded in Milford Sound following the massive landslide  were calm about their predicament and making the most of their extra time in the popular tourist spot, a lodge assistant manager said this morning.

Milford Sound Lodge assistant manager Anna France said six guests were flown out yesterday  and another 12 were due to fly out today with Fly Fiordland, who were offering discounts to those who wanted to leave.

The 21 guests who had stayed at the Milford Sound Lodge last night were calm about the situation, she said, with some using the time to go out for a kayak or a walk.

For the people remaining at the lodge - which has capacity for 150 people and 40 campervans - there was plenty of food and supplies, she said.

Most people had been out to the pub the night before, she said.

"Everyone’s embracing this. It’s been good fun." This was the third time this year the only route out of Milford Sound was cut off, she said. Staff at the lodge - the only accommodation for independent travellers at Milford - were accustomed to road closures.

Milford Helicopters pilot Sean Snow said the company made six trips in and out of Milford Sound yesterday.

Fifty people were airlifted out of Milford Sound. Forty people on an overnight cruise with Real Journeys were among tourists and workers stranded when an avalanche threw 200-tonne rocks across the only road into the village. 

Real Journeys chief executive Richard Lauder, who was also stranded in Milford Sound, said two helicopters airlifted about 50 people across the slip yesterday.

Some abandoned their rental cars in the village after talking to their travel insurers and rental car companies, he said.

A small number of people decided to stay in Milford Sound. 

"Anyone who wanted to get out, got out, and anybody who wanted to stay did."

Those who flew over the slip were then bused to Te Anau or Queenstown. 

Lauder said Milford Sound experienced about 10 days of road closures every winter, and had seen about seven so far this year.

The closures usually only lasted for 24 hours.

Robinson said because the road had been closed at 4pm Friday due to avalanche risk, most visitors had already left Milford.

People who been staying in Milford Sound were given the opportunity to leave before the road was closed, he said.

Staff and visitors in Milford would be kept informed of timing as the assessment of the situation continued.

- © Fairfax NZ News