Drugs with an estimated street value of four million euro have been seized by gardai in two separate operations within 24 hours.
In Co Galway, cannabis plants worth about 2.5 million euro were found at a business premises in Tuam on Saturday morning.
Two men - one aged in his mid-40s, the other in his early 50s - were arrested.
The operation in the west of the country follows a raid in Co Meath on Friday night when 1.5 million euro worth of cannabis was seized.
The plants and herb were discovered by gardai at a business premises in Kells.
A 53-year-old man and 43-year-old woman were detained during that raid.
In Tuam, approximately 3,000 plants at various stage of growth were seized along with drug-growing paraphernalia.
Gardai described it as a " sophisticated cannabis-growing operation".
In Kells, officers said a large cannabis cultivation operation was discovered.
All four arrested people are being held under Section 2 - Criminal Justice (Drug Trafficking) Act 1996.