The joint paramilitary task force has arrested a man in Newtownards.
Police carried out a search in the Mark Street area of the town on Monday seizing a firearm and ammunition
A 27-year-old man was also arrested and remains in police custody at a Belfast police station.
The paramilitary crime task force was set up as part of the Executive's action plan to target criminal gang activity in Northern Ireland with millions committed to it by both Stormont and Westminster as a result of the 2015 Fresh Start agreement.
It is a collaboration between the PSNI, the National Crime Agency and HM Revenue and Customs.