Some reports said many fans were dressed as sheep on the train
A 24-year-old football fan dressed as a sheep suffered serious burns to his arms and legs when his suit caught fire on a train in Fife.
Aberdeen fans said the man ran ablaze through the carriage as others threw beer on him to douse the flames.
The Edinburgh to Aberdeen service was stopped at Kirkcaldy at about 1900 GMT on Saturday to allow him to be treated.
British Transport Police said a 23-year-old man had been arrested in connection with the incident.
A second man is reported to have suffered slight injuries.
The train was carrying Aberdeen football supporters back home after their side's match against Hibs in Edinburgh.
It is understood a number of the fans at the match and on the train were dressed as sheep.
The train involved, an Arriva cross-country train, was the 1808 GMT service from Edinburgh to Aberdeen.
The fan who suffered burns is said to be in a serious but stable condition in hospital in Kirkcaldy.
British Transport Police said the arrested man was expected to appear at Kirkcaldy Sheriff Court on Monday.