GARDAI will resume their search this morning of an area close to the north Louth Border where 21 mortars, frames and mortar tubes were discovered yesterday.
The weapons were found during a planned search of farmland close to Hackballscross.
The land, which is just yards from the Border, is understood to belong to a resident of Northern Ireland.
The find is the latest in a series of successes claimed by the security forces against the IRA, and follows significant discoveries of armaments in Britain as well the Republic.
Last month the Garda found a rocket launcher and assorted ammunition near Dundalk while a large quantity of explosives was found on a farm in Co Laois in June.
Last week raids by British police in London and Sussex yielded 10 tonnes of homemade explosives.
Early yesterday gardai began searching houses and lands near Ballybinaby, Hackballscross. They discovered the mortars in a bunker behind the houses in the early afternoon.
The Garda said the bunker was approximately 5ft deep, and contained 21 mortars and eight mortar frames. Five of the frames had three mortar tubes mounted on them, and three had two tubes attached.
No explosives or firearms were recovered.
The Garda described it as "a very significant find". Technical examinations today are expected to reveal how long they were in the bunker.
Gardai have been carrying out a number of searches in the last week of an area stretching from Feede to the Faughart road.