Floodwaters are still rising in the Italian-speaking canton of Ticino, which has had more heavy rain. Parts of the city of Locarno are underwater, and more people have had to be evacuated from vulnerable areas.
The rising waters of Lake Maggiore, which have already flooded the Piazza Grande in the centre of Locarno, are now threatening the city's fuel supplies.
The local authorities are warning that the city's fuel tanks are at risk of being dislodged by the sodden earth. The emergency services are on a state of high alert.
Elsewhere around the lake, more villages and towns have been submerged by the rising waters, which reached record levels on Tuesday, surpassing those of 1993, when the canton recorded its worst floods in a century.
Meteorologists are warning that further sporadic rainfall is expected.
Around 2,000 people have already been evacuated from areas in and around Locarno, as they have become progressively submerged. Some areas are now completely cut off.
swissinfo with agencies