Police in the North estimate herbal cannabis seized in County Down yesterday was worth 1.47 million euro
Officers describe it as the largest seizure for some time.
Two 68 year old women and a 72 year old man arrested as part of the investigation, have been released on bail pending further police enquiries.
A 32 and a 37 year old man remain in custody, along with a 42 year old woman.
A sixth person, a 42 year old woman, has also been arrested on suspicion of a number of drugs charges.
The drugs were seized in Dromore following a cross border operation involving the PSNI, Gardai and Revenue Customs Service.