Gardaí seized a firearm and arrested two men near an abandoned car on the M50 on Wednesday.
The men, aged 33 and 20, were found a short distance away from where the black Volkswagen Golf was left on the N2 underpass at the M50 junction, in the direction of the city centre.
Gardaí from Finglas said they discovered a firearm during the search which took place at about midday.
The men were arrested at the scene and taken to Finglas Garda station. They were detained under Section 30 of the Offences Against the State Act.
Gardaí are appealing to anyone who may have witnessed the Volkswagen Golf in the area to come forward.
Any road users on the N2 headed in the direction of the city centre between 11.45am and 12.15pm and who may have dashcam footage is also asked to contact to gardaí.