A man and a woman, both in their 30s, have been arrested as part of an investigation into irregularities at the Passport Office.
Both are employees at the Passport Office, in Molesworth Street, Dublin.
They were taken to Pearse Street Garda Station. The woman was released this evening and a file will be prepared for the Director of Public Prosecutions.
The man remains in custody.
The Department of Foreign Affairs confirmed that a joint Passport Service and garda investigation has been taking place at the Passport Offices in Molesworth Street and Balbriggan.
In a statement the department said the Passport Service launched an investigation in Autumn 2013 when internal checks revealed irregularities in the processing of three passports.
The Garda National Bureau of Criminal Investigation was informed and a joint investigation was launched.
The statement said: "The Passport Service takes the issue of passport fraud very seriously and has strengthened measures to identify and prevent potential fraud.
"Customer services provided by the Passport Service will not be impacted.
"As this is an ongoing enquiry it is not possible to provide further comment."
Gardaí have said the arrests are part of an ongoing investigation being conducted by the Investigation Section of the National Bureau of Criminal Investigation into fraudulently obtained Irish passports.