Three people questioned in connection with the discovery of a number of suspect devices in Cork city last year, have been released from custody.
A file will be prepared for the Director of Public Prosecutions.
A man and a woman in their 30s were detained in Kells, Co Meath yesterday, while another man in his 20s was arrested in Mallow, Co Cork.
They were held at the Bridewell, Mayfield and Gurranabraher garda stations.
One of the devices was found under a car at Mervue Lawn in Ballyvolane on 11 March last year.
Up to 100 houses had to be evacuated at the time.
An army bomb disposal officer sustained minor injuries during the operation and had to be treated in hospital.
Another device was found in a house at Kilnap Place in Farranree last July.