A 500-tonne boulder that crashed onto Milford Road in Fiordland last week was blown apart with explosives today.

Enormous boulders were brought down by a landslide on Friday, blocking the only road to the popular tourist area.

The slip had covered about 200 metres of the road. The biggest rock had now been successfully blasted and cleared away, along with other rocks, New Zealand Transport Authority Southland area manager Peter Robinson said.

Among the equipment being used to clear the debris were drilling rigs and two large excavators.


Recommendations from geotechnical experts who inspected the main slip were being followed to ensure the safety of workers, Mr Robinson said.

It could be some time before the cost of the work was known.

It was hoped one lane would be open to traffic tomorrow but the weather could still get in the way of their plans.

"The issue is we still have some rock which, in heavy rain, may be an issue. It's meant to rain hard later and if it becomes too heavy we'll have to withdraw from the site because of the risk of further landslides," Mr Robinson said.

Fortunately, the road had been closed because of an avalanche risk when the slips happened, so tourists had already been asked to leave the area.

Mr Robinson said Milford residents were well set up to live without the road.

Milford Sound Lodge manager Japke Doodeman said yesterday the closure meant the lodge was losing about 30 people a day.

"But considering all the boat companies and kayak companies that [usually] have buses coming in on a daily basis as well, it's quite a lot more than that."

There were 26 people staying at the lodge when the road was closed. Most had been flown out of the area.

Milford was "regularly" cut off, and the business was prepared when it happened, but the weekend slip was "massive", she said.

"Over winter it does happen a bit more often, definitely towards the spring season because that's when the avalanche risk gets higher."