Upwards of 1,000 foreign nationals are being sought by Garda immigration officers, the head of the Garda National Immigration Bureau has said.
Speaking following the arrest over the weekend of 16 foreign nationals who had made applications for asylum under false names after initial rejections, Chief Supt Martin Donnellan said there would "certainly" be further arrests of people on the same grounds.
The 16 people, four Nigerians and 12 from eastern Europe, were arrested on Saturday morning in Dublin, Cork, Ennis and Co Galway. Some of them were held at Garda stations, with others being detained in Mountjoy Prison in Dublin. All were men.
Arrangements were being made for their deportation as soon as possible, said Chief Supt Donnellan. The individuals had made asylum applications a number of years ago, which had been refused.
"They went underground and then reapplied under different names. There were deportation orders on them and it is our job to find them and detain them and send them home," said Chief Supt Donnellan.
It was not always straightforward to locate people on whom deportation orders had been made and there were "ongoing searches and investigations" to this end.
"It's not always easy to find them," he added.
There were a "huge number" of foreign nationals in the State using false documents, he went on, adding that great ingenuity often went into the production of false passports and identity documents.
Mr Peter O'Mahony, chief executive of the Irish Refugee Council, said the fact that just 16 people had been arrested showed the perception that there were fraudulent asylum applications "on a massive scale" to be untrue. "If this was a massive crackdown, 16 is hardly a huge number," he said.
Chief Supt Donnellan said the introduction of mandatory fingerprinting of all asylum applicants in November 2000 had reduced the scope for people whose asylum application had failed to reapply under a different name.
Prints are checked against all previous applications.
Since November 2000 any asylum-seeker over the age of 14 who refuses to be fingerprinted may be detained and faces deportation.
The 16 arrested over the weekend had all made their initial applications before November 2000, said Chief Supt Donnellan.
"Quite a lot of deportation orders were issued on people who made applications before November 2000.
"A lot of our work is clearing that backlog. I can't say exactly how many, but there would be over a thousand deportation orders outstanding."
He said more than half of those who applied for asylum here did not pursue their application.
"They apply when they arrive and then don't show up for interview. The only logical conclusion is that they are using the asylum process to transit through the country or to enter it. That is a real problem."
By the time deportation orders were made, some spurious applicants could be long gone from their port of entry or from the State itself.
Mr O'Mahony agreed that at least 10 per cent of asylum applicants left the State soon after. "This shows that Ireland is not the attractive haven or paradise for asylum-seekers that many would like to have us believe," he said.
The weekend's arrests were part of the ongoing work of the Garda National Immigration Bureau.
"You can expect more arrests over the next weeks," said Chief Supt Donnellan.