Ten Chinese men are being held in police custody and are facing deportation for working and staying in New Zealand unlawfully.
An Immigration New Zealand (INZ) operation focusing on the construction industry found the men during a visit to a construction site in central Auckland yesterday.
They were found to have been unlawfully in the country for periods ranging from 17 months to more than three years.
Immigration New Zealand (INZ) said arrangements were being made for their deportation to China.
In a statement, it said they also met with lawful migrant workers to check they were being treated fairly by their employers.
"INZ has also provided education packs to employers to ensure they have all the information they need about their obligations."
INZ's deputy head Stephen Vaughan said the operation was about being proactive in preventing migrant exploitation and ensuring businesses followed the rules when using migrant labour.
"The illegal use of migrant labour poses a real risk of migrant exploitation, which is something INZ is keen to combat. It's also a disadvantage to businesses that follow the rules and are doing the right thing in their use of foreign workers," he said.
Vaughan said the operation involved one employer.
He declined to comment on possible charges.