Ammunition and a suspected mortar tube have been found by gardaí during searches of land in north Co Louth targeting dissident Republican groups.
The haul has been described as "significant."
Gardaí say the ammunition is of varied calibre. The suspected mortar tube is to be examined by garda ballistics experts.
Members of the Special Detective and Emergency Response units are taking part in the planned operation around the village of Omeath.
Officers say the investigation is still live.
Searches are continuing across lands along the Cooley Peninsula this afternoon and are to continue tomorrow.
The Army Explosive Ordinance Disposal team is at the scene and a cordon is in place.
No arrests have bee made.