Cannabis herb worth over half a million euro was seized yesterday in Co Roscommon.

Members of the Roscommon & Longford Divisional Drugs unit searched a house in Frenchpark under warrant at about 3.30 yesterday afternoon.

They discovered a sophisticated growhouse in the residence and external sheds, and seized a total of 139 cannabis plants, with an estimated street value of €112,000.

Also, about 22.5 kg of vacuum-packed cannabis herb was seized, valued at €480,000.

A man in his 20's was arrested and is being detained at Castlerea Garda Station under Section 2 of the Drug Trafficking Act.

Gardai say their investigations are ongoing.