The entire network of the Swiss Federal Railways has shut down due to a power failure, leaving tens of thousands of commuters stranded.
A Railways spokesman said the power failure began in the southern canton of Ticino, but could not say what caused it or when trains would begin running again.
The entire network collapsed at 17.45 - the first time the Federal Railways has suffered such a breakdown in its history.
International intercity trains passing through Switzerland have also been affected, as well as train lines of smaller Swiss railway companies.
Railways spokesman, Roland Binz, said the amount of voltage passing through the railway lines’ contact wires in Ticino dropped considerably, causing the shutdown.
He said it then spread to the whole system for an unknown reason.
Binz said emergency crews acted quickly to remove trains that had been stuck in tunnels.
The collapse of the network has occurred during a heat wave.
He said passengers had been evacuated from all of the stranded trains in order to provide them with fresh air since the the trains' air conditioning systems are also no longer operational.
At Bern station, hundreds of people were milling around waiting for news.
A team of Railways’ employees were on hand to provide what little information they could, and to hand out bottles of mineral water to thirsty passengers.
One staff member, Kathrin Pieren, told swissinfo’s correspondent at the station that she had no information about what had gone wrong and when services might resume.
"We have no idea what’s wrong, or how long it’s going to take. At the moment we are trying to organise buses to the major cities to replace the trains."
Several hundred people were watching the departure board, which had evidently stopped working at the same time as had the trains, said our correspondent.
Some people were holding up hand-scribbled signs, seeking fellow passengers who might be willing to share a taxi. One man was asking for people to join him in a taxi to Basel.
A stranded woman passenger told our correspondent that she was "amazed that this could happen in Switzerland. What can we do? We just have to wait".
Another passenger, who gave his name as Michel Brönnimann, was philosophical: "These things happen. Fortunately, I’m not in a hurry, but I feel very sorry for all the other commuters."
Our correspondent said some local trains, not operated by the Federal Railways, were operating normally on the regional lines from Bern to Solothurn.
swissinfo with agencies
The Federal Railways transports about 700,000 passengers a day.
The Railways increased the number of regularly scheduled trains by 12% at the end of 2004.
The country's railway network has 5,100 kilometres of track, normal and narrow gauge.
In compliance with the JTI standards