According to Irish Rail, on Monday evening its Heuston-Cork service was delayed after the driver received a report of drug use occurring on the train.
Gardaí attended at Hazelhatch train station near Celbridge and the train continued on its journey after a delay of about 30 minutes.
No drugs were found, but general secretary of the National Bus & Rail Union (NBRU) Dermot O’ Leary has described anti-social behaviour as a common problem on public transport, which is “out of control”.
In a letter to Irish Rail chief executive, seen by, Mr O’ Leary describes the “frustration of the NBRU”, which has repeatedly raised concerns over anti-social behaviour.
“The NBRU is black and blue in the face from raising issues associated with anti-social behaviour aboard our trains over recent years.
“[Monday’s] incident, in the middle of Pandemic Level 5 restrictions, where essential travel only is permitted, is frankly off the scale,” he said.