A quantity of explosive, found in a flat on Dorset Street in Dublin this morning, was brought into Ireland following a failed security operation in Slovakia.

The explosive was one of eight pieces of contraband planted by the authorities in the luggage of unsuspecting passengers at Bratislava Airport in Slovakia last weekend as part of a test of security procedures.

Seven were detected by airport security, but the eighth - 90g of research development explosive or RDX - was put in the luggage of a Slovakian electrician who lives and works in Dublin.

The 49-year-old unwittingly brought the material to Dublin when he returned from Christmas holidays.

Gardaí were eventually alerted this morning following a call from police in Bratislava and the flat on Dorset Street was sealed off.

During the operation, the adjoining homes and businesses were evacuated as the Army Explosive Ordnance Disposal unit removed the explosive for further analysis.

Both Gardiner Street and Lower Dorset street were closed off for about an hour.

The Slovakian man was arrested at the scene, but gardaí are now satisfied that he is innocent and he was released from custody this afternoon. He will not face charges.

The Department of Foreign Affairs said the Slovakian Minister for the Interior has conveyed his Government's profound regret for this incident to the Justice Minister Dermot Ahern.

Minister Ahern said he was very concerned about the fact that the gardaí were not alerted for three days and has asked for a full report.

Garda Commissioner Fachtna Murphy has appointed Detective Chief Superintendent Martin McLaughlin to establish the full background to this incident.

The Slovakian Minister has told Minister Ahern that his government will cooperate fully with the Garda investigation.