Transport police were called to deal with two disturbances on trains through Fife.
A train worker was threatened by a passenger, described as a man in his forties with a bushy beard, during one of the incidents on Sunday afternoon.
It happened on the Glenrothes with Thornton service which left Edinburgh at 5.16pm.
There were also reports of sectarian singing on the 5.34pm service from Edinburgh to Dundee.
Officers from British Transport Police were called and intercepted the trains at Kirkcaldy station.
NEW: Due to passengers causing a disturbance on board a train at Kirkcaldy, services through the area will be cancelled, delayed or revised. @BTP are responding and we’re assisting them with investigation. Further info as we get it. ^CT pic.twitter.com/RaOqMNad6V
— ScotRail (@ScotRail) December 2, 2018
A British Transport Police spokesperson said: “Officers were called to Kirkcaldy station at 6.30pm last night after reports of a disturbance on the 5.16pm train from Edinburgh to Glenrothes with Thornton.
“A man made violent threats to a member of staff on board the train. The man was in his forties and approximately 5ft 10ins. He had dark hair, a bushy beard and was wearing a blue waterproof jacket.”
The incidents happened within minutes of each other.
No arrests were made in either case.
However, transport police would like to hear from anyone who witnessed the incidents or has any information.
The spokesperson added: “Officers were called to Kirkcaldy station at 6.28pm last night after reports of sectarian singing on the 5.34pm train from Edinburgh to Dundee.
“Officers attended and are making inquiries into this incident as part of an investigation. No arrests were made.
“Were you on the train? Did you see anything? Please call 0800 40 50 40 or text 61016 quoting reference 456 of December 2, if you have any information which could help officers investigate.”
The disturbances led to services through Fife suffering disruption, causing more headaches for rail travellers amid delays and cancellations caused by crew shortages.