The gang involved is said to have threatened passengers with planks of wood
The Justice Minister says "every effort" is being made to identify those behind a 'graffiti attack' on a DART train in north Dublin earlier this week.
A gang of people wearing balaclavas sprayed graffiti all over a DART carriage in Clongriffin on Tuesday night.
Those involved blocked doors from closing, preventing the train from leaving the station.
They are also said to have threatened customers with pieces of wood.
Responding to the incident, Irish Rail said: "While we battle with graffiti all the time, we have never had anything of this scale"
Speaking in the Dáil, the Justice Minister Charlie Flanagan said gardaí are investigating.
He said: "Every effort is continuing locally to identify those involved.
"I'm further advised that very close contact is being maintained with local and senior management of Irish Rail and other transport providers."
Meanwhile, the DART incident and an rise in joyriding has prompted a call for more gardaí in the Clongriffin and Darndale areas.
Local Sinn Féin TD Denise Mitchell says there are not enough officers to share the workload.
She observed: "I do want to acknowledge the hard work that the gardaí are doing on the ground - but Garda numbers are down in the area.
"We're calling on the Government, and particularly the Minister for Justice, to ensure that our communities are safe by providing adequate resources."