Seven people are awaiting deportation after Home Office officials raided properties in Belfast and Co Down.
Illegal immigrants from Malaysia, Nepal, Bangladesh and Pakistan were arrested and have been taken to a detention centre in Larne, Co Antrim.
Mike Golden, for the Home Office, said: “Foreign nationals who are in this country illegally should be in no doubt that they will be caught, arrested and removed from the UK.
“We are determined to crack down on immigration offenders and anyone found living or working here illegally is liable to be detained and removed.”
The arrests followed raids on a number of restaurants and takeaway shops in Belfast, Lisburn and Newry.
The businesses have each been served with a penalty notice for employing illegal workers and could face a fine of at least £10,000 if they are unable to provide evidence that the correct pre-employment checks were carried out.