A large scale security operation was launched on Wednesday night.
Shortly before 6.30pm yesterday Gardaí received reports of a man on a commuter train, arriving into Connolly Station, that had been spotted with a suspected gun.
He's not alleged to have threatened passengers but it led to teams of armed Gardaí rushing to the scene, while the station was evacuated and services suspended.
A security sweep was carried out and a man in his 50s was arrested before the station was later declared safe.
He's being detained at a Garda station in the capital and can be held for up to three days for questioning.
Meanwhile Gardaí say they're aware of fake news being spread online in relation to the incident - and are asking the public to independently verify information shared on social media and through messaging apps.
