As much as 3,000 cubic metres of rock collapsed on Tuesday over the Gotthard railway. Two rail workers were pulled injured from the debris but a third, 29-year-old Werni H, remains missing, online news site Blick reported.
The rock came tumbling down, covering the tracks near Gurtnellen in canton Uri. The men were working at the time to secure the rocks from exactly this kind of eventuality.
A threat of further rock-fall meant that rescuers could only send down search dogs alone. They have also installed a radar system that tracks even the slightest movement of rock, and may decide to trigger more rock fall with explosions before they consider it safe.
It is estimated that approximately 500 truck-loads will be needed to remove the amount fallen so far, online news site 20 Minuten reported.
The chances of finding the young father Werni alive are diminishing.
Another major landfall happened just three weeks ago at Preonzo in Ticino. This slide, which comprised approximately 300,000 cubic metres of rock, was predicted and no injuries resulted.
It is thought that the rock fall at Gurtnellen resulted from the increasing pressure brought to bear by water in the rock, eventually causing the rock to break.
In the meantime, one of the country's most important transport arteries has been closed off, with replacement bus services being scheduled in order to cope with a closure officials expect to last for a month.