Five men are being questioned over suspected dissident republican activity, detectives said.
They were arrested after a raid on a house in a rural area outside Monasterevin, Co Kildare.
Gardai said no explosives were found at the scene but piping was being forensically examined.
Three men aged in their 20s, 40s and 50s were initially arrested earlier in the day.
They are being held at Naas Garda Station.
A 55-year-old man was later arrested and brought to Tullamore Garda Station. Another man, aged 41, was taken into custody and questioned at Newbridge Garda Station.
All men are being held under section 30 of the Offences against the State Act.
The Garda's Special Detective Unit and Emergency Response Unit backed up local officers during the operation.
The scene was sealed off for a technical examination.