Three men were being questioned tonight after the drugs squad seized 500 cannabis plants in a raid.
The haul, with an estimated street value of €200,000, was found in a property in a rural part of Co Carlow, near Leighlinbridge.
Paraphernalia used for growing the plants was also recovered.
The raid was carried out by the Garda National Drugs Unit and local officers from Carlow garda station.
The three men, all aged in their 20s, were arrested at the scene and detained under section two of the Drug Trafficking Act.
They can be held for up to seven days.