Gardai and Revenue officials have confirmed that 4.5kg of herbal cannabis has been seized at post depot on Friday.
It is understood that customs officials seized the quantity drugs worth an estimated street value of €90,000 at Portlaoise Mail Centre.
Official say the herbal cannabis was concealed in a parcel of dried fish that had come from Mozambique with address earmarked to a premises in Dublin.
Gardaí say an investigation into the discovery is currently ongoing.