Two men are still being questioned after they were arrested in Louth yesterday by gardaí investigating dissident republican activities.
The men were detained at a house in Hackballscross at about 1pm following searches of the house and a number of outhouses.
The two in their 50s are being detained at Balbriggan and Drogheda Garda stations under Section 30 of the Offences Against the State Act 1939.
The area around the house was sealed off, and an Army team arrived at the scene at 4.50pm yesterday. It examined what a Defence Forces statement said was a "substantial" quantity of material over six-and-a-half hours.
Components of an improvised mortar system, which included explosive material, were made safe at the scene, and the remains were handed over to gardaí. The Army also seized a large amount of fertiliser.
The scene was declared safe at 11.30pm last night.