British Transport Police detectives are appealing for witnesses to a fight involving three men on board a train from Chester to Colwyn Bay on Saturday 14 July.
The incident is believed to have happened at approximately 9.20pm in the middle/rear carriages of a busy Arriva Trains Wales service, near Colwyn Bay.
A man was left with minor injuries to his face as a result of this incident.
The fight happened on board the 5.21pm service between Cardiff Central and Holyhead.
A spokesperson for British Transport Police said:
“Officers are conscious that this was a busy service and a number of passengers on board would have witnessed what happened.
Were you on the train at the time? Did you see anything? Call 0800 40 50 40 or text 61016 – quoting 253 of 27 July – if you have any information which could help the investigation. Alternatively, you can ring Crimestoppers anonymously on 0800 555 111.”