A woman needed hospital treatment after a brawl on a night-time train from Newcastle.
British Transport Police (BTP) are appealing for information about the incident, on a train travelling to Carlisle.
Our customers and staff have the right to travel safely, and we are working with British Transport Police to ensure those responsible are held accountable.Martyn Guiver, Northern Rail
It was the 9.18pm Northern Rail service on Saturday, August 8, and the fight erupted at about 10pm.
Investigating officer Pc Amanda Timlin said: “A fight broke out between a group of men and women on board the service.
“One woman was left with a split lip requiring eight stitches.
“We have launched an investigation into the incident, and have undertaken a number of inquiries.
“We are now trying to determine exactly what happened on the train, and I would urge anyone who was travelling on the service and witnessed the incident to please come forward and speak to us. Your information could be vital.
“We believe a number of passengers who may have seen the fight left the train at Prudhoe and Riding Mill.”
Martyn Guiver, head of crime management for Northern Rail, said: “We have a zero-tolerance policy to disorder on our trains.
“Our customers and staff have the right to travel safely, and we are working with British Transport Police to ensure those responsible are held accountable.”
Anyone with information is asked to contact British Transport Police on 0800 405040, or text 61016, quoting reference PSUB/B4 of 19/8/2015.
Information can also be passed anonymously to the independent charity Crimestoppers on 0800 555 111.