Three men and a woman arrested by gardaí investigating alleged paramilitary activity are still being questioned.
The suspects, all in their 40s and 50s, were arrested in the Dundalk area yesterday morning.
All four are from the local area, a Garda spokesman said yesterday.
The arrests were made under anti-terrorist laws introduced after the "Real IRA" bombing of Omagh on August 15th, 1998, in which 29 people were killed and 300 injured.
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They are being held under Section 30 of the Offences Against the State Act and are being questioned at Balbriggan and Drogheda Garda stations.
The four can be held for up to 72 hours without charge under the act.