GARDAI believe that pipe-bombs found in a derelict house were left there to be collected by criminals.
A number of local residents were evacuated from an area on the outskirts of Dundalk, Co Louth as gardai and the army bomb disposal team dealt with the incident.
The alert began about 2.30pm yesterday when gardai went to investigate suspicious activity at the building at Haggardstown, about 2km south of Dundalk on the old Dublin road. They found the suspicious devices and called the army bomb disposal team.
The Defence Forces press office confirmed the four viable devices were "made safe in situ without the need for a controlled explosion and will be removed to a secure military location for further examination."
The scene was declared safe at 6.15pm.
A gang in north county Dublin is believed to be producing the bombs for use by other criminals and the scene of the alert yesterday is just a few minutes drive from the M1 motorway, making it an easy location to access.