GENEVA, Jan. 24 (Xinhua) -- Eight men trapped in the Hoelloch cave network in Switzerland's Muotathal valley since Jan. 21 can only be rescued this weekend due to heavy rainfall, Swiss media reported Wednesday.

They are unhurt and are currently stuck in a water-tight bivouac in the cave whose name is German for "hell hole," the Swiss News Agency, SDA, reported.

The group of cavers are aged between 25 and 55 and had entered the cave system, one of Europe's biggest, on Saturday morning and planned to leave the following afternoon.

However, a sudden onrush of water surprised them during their excursion with a professional guide.

A specialist search and rescue team has reached them, but is waiting for the water to recede before making their way out of the cave along a three-kilometer-long route.

Specialists are continually assessing the predicament of the trapped men, but police said it is likely that they will remain trapped until the weekend when the weather is forecast to make the task easier.

The trapped men have enough materials and food to survive inside the bivouac, where the temperature is 6 degrees Celsius.

The Hoelloch cave system in the central Swiss canton of Schwyz is known as one of Europe's biggest cave systems due to its length estimated to be at least 190 kilometers, but could possibly be 10 times longer, said reports.

In the past, cavers have been trapped, particularly in winter when most expeditions take place because of low water levels.