DUBLIN (AP) — A Slovak man unwittingly carried hidden explosives on board a weekend flight to Dublin as part of a Slovakian airport-security test that went awry, Irish officials said Tuesday.

The Slovak interior minister, Robert Kalinak, expressed “profound regret” to the Irish government for the oversight and the three-day delay in alerting Irish authorities.

Dublin security officials said it had been foolish for the Slovaks to hide bomb parts in the luggage of unwitting passengers under any circumstances.

Security experts said the episode illustrated the inadequacy of security screening of checked-in luggage, the very point the Slovak authorities had sought to test when they placed real bomb components in nine passengers’ bags on Saturday.

Eight were detected. But the ninth bag, containing about three ounces of a plastic explosive, RDX, traveled undetected through security at Poprad-Tatry Airport in central Slovakia onto a Danube Wings aircraft. Danube Wings, a Slovak airline, inaugurated service to Dublin last month.

The Dublin Airport Authority confirmed that no incoming baggage is screened in Dublin. The man who carried the explosive did not find out about it until the Irish police, acting on a Slovak tip, raided his apartment in Dublin on Tuesday morning.

The police said they were initially led to believe that the man might be a terrorist, until Slovak authorities admitted that they had planted the explosive.

Justice Minister Dermot Ahern said the Dublin police eventually confirmed that the explosive “was concealed without his knowledge or consent” as part of an airport security exercise.

A major north Dublin intersection was shut down and neighboring apartment buildings were evacuated as a precaution while Irish Army experts inspected the explosive. The man was released without charge after several hours’ detention.

An Irish Army spokesman, Commandant Gavin Young, said the explosive had posed no threat to passengers because it was stable, meaning it would not explode on its own if hit or placed under pressure, and it was not connected to other essential bomb parts.

The Dublin Airport Authority said it periodically tested the skills of baggage screeners, but using only bags under the control of security officers, not civilian passengers.