Diamorphine worth £300,000 was seized at Dublin Port on Saturday following a tip-off to gardai.
Gardai arrested a man who it is believed had just disembarked from a boat at 10.15 p.m. and was allegedly carrying the drugs.
In another drugs find, 10 kg of cannabis resin worth £100,000 was discovered at 2 p.m. on Saturday in a wooded area at Mountain Barracks, Kilworth, near Fermoy, Co Cork.
Gardai in Navan arrested two women and seized ecstasy and cannabis in a raid on a new apartment in the town centre on Saturday night.
The women were arrested and interviewed about supplying controlled drugs.
A Garda spokesman said a total of 11 people were questioned about the seizure and a file will be sent to the DPP.
It is believed that nine of the people detained by gardai were customers and the raid by gardai from Navan and Drogheda, with assistance from the Garda Dog Unit, prevented the possible sale of the drugs over the weekend.