Two avalanches are blocking the Milford Road. Crews are trying to clear them in the hope of reopening the route on Thursday.
About 50 tourists, in 34 cars, were escorted out of Milford Sound on Monday, before Tuesday's snow as it was anticipated the avalanches could happen.
The Transport Agency says the avalanches are some of the biggest for many years, with one about 10 metres deep covering several hundred metres of the road.
Southland area manager Peter Robinson says a lack of snow this season has created the perfect conditions for avalanches.