Employers hiring migrants who are not lawfully entitled to work for them can be prosecuted, and, if convicted, face a penalty of up to $50,000.
"We hope that this will be a warning to employers that they must make basic checks on seasonal workers before they employ them. It is also a warning to people who do not comply with their visa conditions; they are vulnerable to exploitation by unscrupulous employers," said Mr Blakemore.
INZ is urging people who are working in breach of their visas to come forward and discuss their individual circumstances, by ringing the INZ's freephone number 0508 55 88 55.
The eight workers are in custody in Whangarei pending deportation.