Gardaí are to carry out further searches today of a wooded area near the Border for hides being used by dissident republicans to store arms.
Around a thousand rounds of ammunition and a mortar tube were found in two hides about 6km from Omeath, Co Louth, yesterday.
The assorted ammunition was for use in small arms and semi-automatic rifles. They were concealed in lunch boxes stashed in a barrel, which had been buried in the ground.
The empty mortar tube was found wrapped in plastic in a separate hide nearby. The were both in a wood, about 1km off the Omeath to Flagstaff road.
The finds followed a search operation by gardaí, with the aid of a digger, as a result of intelligence gathering by officers.
Garda personnel from the Louth division were backed up by anti-terrorist officers from the Special Branch and the Emergency Response Unit.
A senior officer told the Irish Independent last night that the ammunition and tube had been stored there for at least a year, but described the find as significant.
Officers are satisfied that the material belonged to a dissident group, rather than dating back to the Provisional IRA before their ceasefire, and is in good condition.
Gardaí called in an Army bomb disposal team as a precautionary measure, but after a detailed examination the Army decided there was no need for a controlled explosion and returned to barracks.
The tube and ammunition will be handed over to Garda ballistic officers for forensic examination.
The area was sealed off yesterday evening and preserved overnight for a resumption of searches this morning.
Officers declined to say which dissident IRA faction might have used the dumps and the area has been used in the past by a number of groups.
However, the Garda security and intelligence section at headquarters in the Phoenix Park and the Special Branch have ramped up their activity in the Louth-Meath and Cavan-Monaghan divisions in the past couple of months.
This action has been focused primarily on the New IRA, which is thought to pose the main threat to security on the island and is believed responsible for the car bomb explosion outside a courthouse in Derry two weeks ago.
The Special Branch has been sending extra patrols to the Border to combat a feared increase in activity by dissident republicans.
Intelligence indicates that a terror campaign is likely to be re-ignited by the dissidents in the first quarter of the year.
The Garda authorities have responded by deploying additional personnel to Border divisions where the Special Branch presence had been scaled down since the peace process settled in. The patrols are being sent out regularly from the unit's headquarters in Harcourt Square, Dublin.