A man was left needing hospital treatment after a fight broke out on a train between Sheffield and Rotherham.
British Transport Police said an argument between two men on board escalated into a fight between three men.
DC Lee Parsons said: “Violence of any kind on the transport network is unacceptable and we are working hard to gather as much information about this crime as possible.”
The incident happened at 8.40pm on Saturday, October 4.
n Anyone with information is asked to contact BTP on 0800 40 50 40, or text 61016.