Four people have been arrested and a gun and cars were seized during a crackdown on dissident republicans.
The arrests were made as part of investigations into criminal activities in the border area, where security has been stepped up amid fears of a dissident threat at the G8 summit in Enniskillen next week.
A security source said the arrests were not directly linked to the G8.
Gardai said a 49-year-old man and a 43-year-old woman were arrested at Castlebellingham on Monday.
A short time later, a man aged 30 was arrested in Navan.
A garda spokesman said a fourth person, a 38-year-old man, was also detained in Navan on Tuesday.
The men are being held under Section 30 of the Offences Against the State Act at separate garda stations while the woman has been released.
"As part of the operation a commercial premises in Navan was searched along with three residences in Drogheda, Navan and Castlebellingham," gardai said.
"A number of vehicles were also seized for the purpose of search and technical examination. To date, a 9mm handgun has been recovered.
''The operation and investigation is ongoing at this time."