Thirteen sticks of TNT found at Connolly Station this morning could be up to 40 years old, according to gardaí.
The train station in Dublin city centre was closed for several hours after workers found the explosives at about 11.30am.
The area was cordoned off and neighbouring houses and offices were evacuated until the Army Bomb Disposal team declared the area safe just after 2pm.
Iarnród Éireann confirmed the explosives were "historic in nature" and said normal services resumed this afternoon.
Earlier, the army also dealt with suspicious substance found in Dublin Airport this morning.
The substance was destroyed in a secure location on site and the scene was declared safe at 1.30pm.
A sample has been removed to a secure military installation for further examination.