Five people are being held after drugs worth half a million euro were seized at a premises on the Crumlin road.
Four men in their late 20's and 30's were detained in the operation yesterday afternoon.
50 thousand E tabs were discovered during follow up searches in Tallaght and Clondalkin as well as equipment and chemicals used to make the drug.
A woman in her late 20's was arrested in one of the searches in Clondalkin.
