Immigration gardaí say they are powerless to stop well-known European gang leaders involved in organised prostitution and other criminal activity from coming in and out of the country, but regularly pull them in for questioning at Dublin airport.

In recent weeks, a senior garda was on a flight from Romania to Dublin. He noticed a well-known Romanian gang leader on board and telephoned colleagues at Garda National Immigration Bureau (GNIB) at Dublin airport before passengers disembarked.

"He stood out like a sore thumb in a Don Johnson suit [white lightweight suit worn by Don Johnson in Miami Vice]. He's a senior Romanian gang leader involved in organised prostitution and begging gangs," said a senior garda source. "He didn't appear to have any women on board the flight that he was bringing back to work as prostitutes but he did have four heavies. I phoned colleagues at GNIB at the airport and he was hauled in but they couldn't hold him. He's entitled to come and go as he pleases as a European citizen. He would not be kept under constant surveillance here. There just aren't the garda resources for that."

The Romanian criminal was questioned by immigration officers and then allowed into the country. "He is a gang boss over here. There may have been some women on board the flight he was bringing over to work as prostitutes that he was smart enough not to associate with on the plane, or he might have just got lucky," added the source.

Officers from GNIB investigate trafficking into Ireland for sex and labour exploitation as well as illegal immigration. Gardaí from the Organised Crime Unit at the National Bureau of Criminal Investigation probe foreign as well as indigenous gangs' activity and the units' investigations frequently overlap and share intelligence.

At present, there is a major garda probe into the disappearance of 34 Chinese minors missing from accommodation hostels.

The Sunday Tribune revealed that gardaí recently raided the premises of a wealthy Chinese restaurateur in the north-east in search of the children. Gardaí suspect that the missing minors were trafficked into Ireland to work in the sex and labour industry.

Dublin gardaí raided the businessman's three eateries, including a popular high-end restaurant recently refurbished at a cost of €60,000, after receiving intelligence that some of the 34 missing children were in contact with the Chinese businessman.