Gardaí have recovered assault rifles and mortars in an investigation into dissident republicans.
The search was launched in the Scotstown area of Co Monaghan, near the border with the North, after a 43-year-old man was arrested last Wednesday and subsequently charged with IRA membership.
Gardaí said the arms dump contained AK47s, detonators, detonating cord and components for making improvised explosive devices.
The searches are continuing.
Gardaí said the operation involved officers from its anti-terror division, the special detective unit, dog handlers and its armed emergency response unit as well as local officers.
The exact quantities of weapons and explosive devices have not yet been revealed by gardaí.
The searches followed the arrest of Jim Smyth, from Aghalissabeagh, Scotstown, a rural area about a mile from the border.
He was charged with IRA membership at the Special Criminal Court in Dublin on Saturday evening.