Two employees of the Passport Office were arrested as part of an investigation into passport fraud.
It follows investigations by the Department of Foreign Affairs and gardaí.
The Passport Office launched an investigation in May after internal checks revealed irregularities regarding two passports that were being issued.
The Garda National Bureau of Criminal Investigation was informed and a joint investigation was begun.
A man and woman were arrested yesterday in connection with the inquiry.
A 30-year-old man was detained in Skerries, Co Dublin. He was questioned at Balbriggan Garda Station before being released without charge.
A 30-year-old woman was arrested in Dublin and was questioned at Ballymun Garda Station. She has also been released without charge.
Files on both are being prepared for the Director of Public Prosecutions. The garda investigation is ongoing.
Customer services provided by the Passport Office will not be affected by the investigation.
Tánaiste and Minister for Foreign Affairs Eamon Gilmore said no Irish citizen is at risk as a result of the alleged fraud.
Mr Gilmore said the department is taking it very seriously.
He said searches have been taken place at the Passport Office and at other locations.
He said 600,000 passports are issued in Ireland every year and there are very thorough anti-fraud measures in place.