Train services between Dundee and Aberdeen were disrupted after a bull was struck in Angus.
The freight train hit the animal near Carnoustie at around 8.15am on Tuesday, with passengers diverted on to a bus service.
It is understood the bull jumped over a fence on to the line from the nearby East Scryne farm and was killed instantly after being struck at high speed.
The incident caused hundreds of commuters to be late for work, with knock-on effects throughout the day as the line remained blocked.
Network Rail confirmed that the bull had been removed from the track-side and that checks were to be carried out to the train operated by DB Schenker.
The train sustained damage in the collision and was unable to continue any further until an inspection was carried out.
Engineers assessed the vehicle as being unable to continue on safety grounds, and it is likely repairs will be required.
The bus service ran from Dundee to Aberdeen and from Montrose to Dundee/Aberdeen until normal service was resumed at around 2pm.
Rail passengers were advised to expect short-notice alterations to the timetable and delays as a result of the incident
Services were running up to 30 minutes behind schedule due to the requirement for buses.
As a result of the delay some Edinburgh to Inverurie services terminated at Aberdeen.
Passengers travelling north from Arbroath were asked to use Platform One.
A ScotRail spokeswoman said: “We apologise for any inconvenience caused by circumstances outwith our control.”