In a bizarre anti-terror blunder, police in Slovakia used an Ireland-bound passenger as a guinea pig, hiding powerful plastic explosives in his bag to test airport security -- and then forgot to halt him when he boarded the plane.

To make matters worse, three days after the unwitting man arrived home, the Slovak cops alerted Irish authorities -- who thought they might have a terrorist on their hands and shut down part of Dublin as they raided his apartment and arrested him.

The incident, in the wake of the Christmas Day terror attack over Detroit, left Irish officials outraged. Slovak leaders coupled an apology with a blast at the Irish for supposedly overreacting.

The comedy of errors began Saturday morning when a 49-year-old electrician, winding up a holiday vacation in his native Slovakia, showed up at Poprad-Tatry Airport for a four-hour flight back to his new home, Dublin.

He didn't know that police randomly chose him for a test. They slipped two packages of RDX explosive into his bag to see if they would be detected by new sniffer dogs at the airport.

The system worked -- as Janet Napolitano would say -- because a dog smelled something wrong with the bag. But after the dog's handler removed one of the packages, he was called away, and then forgot to return to remove the second parcel.

The man's bag was placed aboard the Danube Wings flight with three ounces of RDX explosive still inside, enough to kill people if not destroy the plane.

The plane landed without incident in Ireland. Officials there said they knew nothing until the Dublin airport got a phone call from Slovakia Tuesday morning.

What was said was unclear, but it triggered an alarm by Ireland's national police. They held the man for three hours as army bomb experts inspected the explosive, still in his bag, and figured out it was all a mixup.