Gardai were called to Shankhill rail station earlier after a fight broke out on board a DART.
The fight was related to a scam in which packets of tissues are placed on seats in an attempt to get passengers to buy them at inflated prices, 98fm reports.
Typically people involved in the scam will harass anyone who touches the tissues until they pay them up to €5.
The 12.55 DART from Bray to Howth was delayed by 20 minutes.
12:55 Bray Howth is delayed at Shankill, due to an incident onboard. Gardai are enroute. Update to follow
— Iarnród Éireann (@IrishRail) February 22, 2018