Several people have been injured after a train came off the tracks near the Swiss village of Tiefencastel, around 30 miles from the ski resort of St Moritz.
The Swiss air rescue service Rega said it had two helicopters at the scene.
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Emergency services were alerted to the crash at 3.50pm on Thursday, Sussex Police said.
WARNING: Some people may find some of the images in this report distressing.
Medical staff who helped during the Westminster terror attack have received a royal thanks for their life-saving efforts.