Gardaí targeting dissident republicans have uncovered a significant cache of explosives and arms along the border, in what is the second linked operation since the start of February.
The operation involved gardaí from the Louth Division and officers from specialist anti-terrorism and firearms units.
A controlled explosion of some of the material discovered was conducted by an Army bomb squad.
The find is part of an ongoing operation against “dissident republican groups”, with the New IRA considered to pose the biggest threat to security forces north and south.
In Garda statement said: “Gardaí have carried out follow up searches at a site in Omeath, Co Louth. On 28 February, as part of a follow-up operation to that conducted on 1 February targeting dissident republican groups, further searches were conducted at lands in an area close to Omeath, Co. Louth.”
The statement said: “The operation involved Gardaí from the Louth Garda Division, Special Detective Unit and from Special Tactics & Operations Command.
“During the operation, gardaí recovered a quantity of explosives, two firearms and a sizable quantity of ammunition of various calibres. An Explosive Ordinance Disposal unit of the Irish Defence Forces later visited the site and some of the material was later destroyed by a controlled explosion.”
It added: “Investigations are ongoing and for operational reasons there will be no further comment."
In the first operation, on 1 February, gardaí uncovered a mortar tube and around a thousand rounds of ammunition.
Fears have been expressed at the highest levels, including by Garda Commissioner Drew Harris, that dissidents plan to exploit Brexit, whether it involves a hard border or a soft border.
Last January, a car bomb exploded outside Derry courthouse, an attack blamed on the New IRA. No one was injured, but the bomb went off shortly after a group of young men walked past the vehicle.
In a statement, the Defences Forces said: "Yesterday evening, following a request from An Garda Síochána, an Army Bomb Disposal Team was tasked to investigate a quantity of explosives found during a planned Garda search in Omeath, Co. Louth.
"In the course of the search, Gardaí found weapons and ammunition along with a small quantity of plastic explosives and a detonator. The team arrived on scene at 6.35pm."
The statement said that, on arrival, a cordon was established for the duration of the operation.
"The quantity of explosives and the detonator were disposed of and the scene was declared safe at 8.25pm."