The thousands of winter holidaymakers are stuck in Zermatt, one of Switzerland's most popular ski stations, the Alpine resort said today.
Heavy snow has blocked all roads and the train leading to the resort - and there have been warnings of avalanches in the area.
Zermatt ski station's website warned that "arrivals and departures are not possible at the moment."
The main access road has been closed since early Monday, while the train was halted on Monday evening.
The Simplon region of Valais was hit by two metres of snow in a 24-hour period, the ATS news agency reported.
Mud and rockslides, as well as flooding, have forced the closure of a number of roads across Valais, as has the risk of avalanches, which regional police have said is currently at the highest possible level.
The town itself is close to the famous Matterhorn mountain.