Gardai in Ennis are questioning a 34-year-old man connection with the discovery of a substantial quantity of commercial explosives and detonators in Limerick city.
The find was made in the Glencairin estate in the suburb of Dooradoyle at 4pm yesterday.
Some 20 cases of commercial explosives were seized along with a number of detonators. They were stored in a van outside the house and in a shed.
Gardai have described the find as one of the biggest of its kind in the State.
The man, who is believed to be originally from Dublin, is being detained under Section 30 of the Offences Against the State Act. He can be questioned without charge for 72 hours.
Investigating gardai are exploring whether the man has connections to dissident republican groups.
The house is being examined by officers from the Garda Technical Bureau and the Army.