Mayo Divisional Drugs Unit together with members from Ballina Garda Station seized €3,000 worth of suspected heroin from a man at Foxford Railway Station on yesterday.
The drugs were detected as part of an intelligence led operation.
A man in his 40s who was travelling by train was searched and found in possession of suspected heroin.
He was arrested by Gardaí at Foxford Railway Station at 4.45pm and detained at Ballina Garda Station.
He has since been released without charge.
A file is to be prepared for the Director of Public Prosecutions in this matter.