GENEVA, Jan. 26 (Xinhua) -- Eight men trapped since Sunday in the Holloch cave network in Switzerland's Muotathal valley -- Western Europe's longest cave -- are free, Swiss police said Friday.

The Schwyz cantonal police said the men had left the cave overnight, coming out on Friday, and were all unhurt, in good spirits, and have returned home.

It had been thought that the group of seven tourists and their guide would have to wait until the weekend to be freed.

But the water level in the cave dropped earlier than expected, a police spokesman told the Swiss news agency, SDA.

The group of cavers aged between 25 and 55 had entered the cave system on Saturday and planned to leave on Sunday afternoon.

A sudden onrush of water, however, surprised them during an excursion with a professional guide.

The Holloch (German for "hell-hole") cave system in the central Swiss canton of Schwyz is known as one of the largest cave systems in Europe due to its length estimated to be at least 190 km, but it could possibly be ten times longer, say local experts.

A specialist search and rescue team reached the trapped men, but the water levels made a rescue impossible at that stage. The group had received psychological support.

Cavers have become trapped there in the past, particularly in winter when most expeditions take place because of low water levels.