A broken rail is suspected to have caused a fatal train crash near Corning, Iowa in the US lon 15 March. One person died when an Amtrak train travelling at 80km/h - well below the 125km/h speed limit - derailed on a straight stretch of track.
The track is owned and maintained by rail freight company Burlington Northern.
Accident investigator Terry Williams, from the National Transportation Safety Board, said the track was visually inspected on the day of the crash, and had had an ultrasonic inspection the previous month. A section of track from the crash site has been sent to laboratories in Washington for examination. A freight train carrying coal had passed the site less than an hour before the crash without reporting problems. A 600m damaged stretch of track has relaid and the route reopened the next day.