Gardaí seized €124,000 worth of cannabis herb in Boyle yesterday.
Members of the Longford and Roscommon Divisional Drugs Unit searched a premises shortly after 12pm discovering a sophisticated grow house.
Three rooms in the building were converted to grow the drug with 55 plants and 4kg of harvested cannabis seized which have been sent for analysis.
A man, aged in his 50s, was arrested during the search and taken to Castlerea Garda Station where he is currently detained.
Investigations are ongoing.