Gardai made an arrest on Friday evening during an operation targeting anti-social behaviour on the DART line.
The force and Irish Rail are clamping down on unruly behaviour on the train line following a number of recent unsavoury incidents.
One person was arrested at Howth Junction DART station are controlled drugs worth an estimated €2,000 were discovered.
Gardai said: "Inter agency security operation targeting anti social behaviour on public transport at Howth Junction Dart Station on Friday evening involving local Garda Units & Irish Rail personnel.
"One person arrested by Gardaí for possession of controlled drugs worth €2k (analysis pending)."
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