Security was being tested at two airports in Slovakia
Irish police have released a man held over an explosives find, after Slovak authorities admitted planting them in his luggage as part of a security test.
The explosives were among eight contraband items placed with passengers at Bratislava and Poprad-Tatry airports last weekend.
The 49-year-old man unwittingly brought the material into Dublin when he returned from his Christmas holidays.
He was arrested on Tuesday morning, but has since been released without charge.
Minister for Justice Dermot Ahern said he was very concerned that Irish police had not been alerted for three days.
Airport security detected seven of the illicit items, but the eighth - 90g of research development explosive - was planted on an Irish electrician.
He unknowingly managed to escape detection at Poprad-Tatry Airport, in north-east Slovakia.
Slovak authorities were reportedly trying to test screening procedures for checked-in luggage by placing items with unwitting passengers.
Ludmila Stanova, spokeswoman for Slovakia's ministry of the interior, says Dublin airport was warned to expect a person carrying explosive samples, and that the passenger was also alerted after his arrival.
"He was supposed to wait for the police to take the sample from him," she told the BBC World Service.
"But for us, it is incomprehensible why they took the person into custody when they knew it was just a sample and just part of training," she told the BBC World Service.
On Tuesday morning the man's flat near Dublin city centre was cordoned off while bomb disposal experts removed the explosives for further examination.
The Irish Army said passengers had not been put in danger because the explosives were stable and not connected to any essential bomb parts.
The Slovak minister for the interior has expressed his government's "profound regret" to Mr Ahern.
An Irish government spokesman said Mr Ahern had "ordered a full report into what has transpired".
Airport security has been stepped up in many countries following an alleged plot to bomb an airliner over the US city of Detroit on 25 December, though it was not clear if the Slovak test was linked to such efforts.