Two Swiss trains collided on Thursday (January 10), injuring 17 people, none of them seriously, and closing the line near the German border, police said.
The two local trains, one travelling from Winterthur and the other from Schaffhausen, crashed just outside the Neuhausen station in northern Switzerland, not far from the German border.
"We're going to look at the train data as soon as possible. And then we're going to control the data from the signal box to see if something wasn't working. We're also going to look at the actual train and the rails to investigate whether something was defective," investigation chief Walter Kobelt said.
Swiss railways said the line was closed and buses were carrying local passengers, while those travelling from Zurich to Stuttgart in Germany would be diverted via Basel.
Police spokeswoman Anja Schudel said 17 people had been injured and nine of them taken to hospital, but nobody was badly hurt. Everybody had been evacuated from the trains, which were carrying a total of 280 passengers, she said.
"All of a sudden everything was moving and shaking and then we noticed that the train had derailed. For a while everything was quiet and then we received the news that our train had collided with another train", train passengers Susanne Neukom and Susanne Friedli said.
Swiss trains have a reputation for punctuality and safety, and fatal train accidents are rare.
The last major accident was in 2010. One passenger was killed and 42 were injured when one of the country's best-known tourist trains, the Glacier Express, derailed at the height of the summer holiday season.