A Chinese man arrested at a fast food takeaway in Lurgan was one of four men detained by immigration officers last week.
The 41-year-old was arrested last Thursday at premises on William Street.
Acting on intelligence, officers visited East Ocean takeaway in William Street, Lurgan where they arrested a Chinese man, who was in the country illegally.
Another Chinese man, aged 43, was arrested at a food outlet in Randalstown while the previous week immigration enforcement officers had arrested two Chinese men in Ballymoney, one a failed asylum seeker aged 47 and the other a 24-year-old who had overstayed his visa.
All four men are now in immigration detention while steps are taken to remove them from the country.
The businesses were served notices warning that civil penalties of up to £10,000 per illegal worker arrested will be imposed unless proof is provided that the correct right-to-work checks were carried out. This is a potential total of up to £10,000 each for East Ocean and Happy Garden, and up to £20,000 for Master Chef.
Employers unsure of the steps they need to take to avoid employing illegal workers can visit www.ukba.homeoffice.gov.uk/business-sponsors/preventing-illegal-working/ or they can call the Employers Helpline on 0300 123 4699.