Two people were left with minor injuries when the slip hit the Howden Hut at 1.30am on Tuesday morning.
All people inside are currently waiting evacuation.
It comes after nearly 200 tourists and about 300 staff spent Monday night trapped in Milford Sound, with the only route in and out closed amid torrential rain that has caused slips and flooding.
Plans are being put in place to evacuate the trapped tourists by midday on Tuesday if weather permits.
UPDATE: 1:45 PM
SH 94 is now expected to remain closed until the end of the week. Due to the damage caused by flooding. The next update will be at 7:30 am tomorrow morning.^SM https://t.co/3e7GuGJNGd pic.twitter.com/XGbngKfWqe— Waka Kotahi NZTA Otago & Southland (@WakaKotahiOS) February 3, 2020
According to MetService forecaster Lewis Ferris, one metre of rain fell in 60 hours in Milford Sound, with 600mm of that in the 24 hours to about 7am on Tuesday.
The heavy rain prompted Emergency Management Southland and Southland District Mayor Gary Tong to declare a state of emergency on Monday afternoon.
MetService also issued a ‘red’ weather warning for the first time, for Westland south of Hokitika and Fiordland north of George Sound.
The red warning is reserved for the most extreme weather events.
🔺 Heavy Rain Red Warning 🔺
This is the first Red Warning we have issued and here's Angus with some details.For more information about Severe Weather see https://t.co/qHyE5zhh6X ^Lewis pic.twitter.com/zZ6eD5j0b6
— MetService (@MetService) February 3, 2020
