Rowdy louts intimidated passengers including young children on a train leaving Edinburgh at the weekend.
British Transport Police (BTP) has appealed for people who filmed the incident on mobile phones to share the footage with them, to help them find the people responsible.
It happened between Edinburgh Waverley and Inverkeithing on Saturday evening.
As the 10.08pm Dundee-bound train pulled out of platform 14, a group of six to eight men started jumping up and down, and banging the carriage roof.
According to other passengers, they were also singing and shouting, and lying in the luggage racks.
BTP said the service was busy, with a number of young children on board, and passengers reported feeling threatened by the men’s actions.
They are examining CCTV footage taken inside the train and at stations along the route.
Constable Jan Langer, the BTP officer in charge of the inquiry, is appealing for anyone who was on the train and can provide information to get in touch.
He said: “The behaviour is not something passengers should be faced with while travelling.
“It is believed that other passengers recorded the incidents on their mobile phones and anyone who has footage is urged to get in touch.”
BTP can be contacted on 0800 40 50 40 or by texting 61016. Information can also be given to the independent charity Crimestoppers on 0800 555 111.