A migrant workers association says it's concerned about the welfare of the 10 Chinese men who were found working unlawfully and now face deportation.
Immigration officers found the men at a construction site in central Auckland yesterday. They have been unlawfully in the country for periods ranging from 17 months to more than three years.
They are now in custody while their deportation to China is being arranged, Immigration New Zealand (INZ) says.
The discovery of the men was the result of an operation by INZ focused on the construction industry.
INZ deputy head of Immigration Stephen Vaughan said one employer was involved in the case and inquiries were ongoing.
Vaughan said the men, aged between 32 to 57, entered the country on visitor visas and at no point had work rights.
"They are unlawful and some of them have been for up to three years, and they were not entitled to work in New Zealand. They're unlawful in New Zealand, and they need to go home."
He said a visit to the site was part of INZ's proactive approach to ensure all employers and migrant workers in the sector were aware of their rights and obligations. Cases like this were not uncommon, he said.
"As part of our construction sector strategy, we're actually looking to get better information and understand some of the challenges in the sector and working along employers to educate them about the legal obligations and ensure foreign nationals are actually working lawfully in New Zealand," Vaughan said.
"We do on occasion visit construction and other sectors and their workplaces and find some really great examples of work practices from employers and employees, but on this occasion, the visit we made yesterday, there was some behaviour that we will not walk past."
He said worker exploitative and illegal employment was a factor and that some firms relied on it to gain a competitive edge in the market.
"I believe there are business models in the construction sector that actually rely on non-compliance and exploitative practices. And this gives them, I think, a little bit of a competitive edge over other businesses who actually comply," Vaughan told Checkpoint.
"I don't think it's just unique to construction... but I believe in the construction sector, there are some areas where the competitive advantage that they get is as a result of exploitative practices."
Migrant Workers Association Aotearoa president Anu Kaloti said her organisation was trying to find out more details and offer any support needed to the men.
Kaloti said more accountability was needed from employers rather than punishing the migrant workers.
"It doesn't matter how many levels of sub-contracting we have, there needs to be a system where each and every tier can be accountable so these workers should not have been allowed to be unlawful in the first place," she said.
"Obviously they were needed here because they were working, so why weren't they given the correct documents? ...they should have been documented with [the correct documents] rather than made unlawful workers ... they should never have been put in that precarious situation of being unlawful in this country."
During the operation, INZ staff have also met with lawful migrant workers and conducted checks to ensure they are being treated fairly by their employers.
INZ said education packs had also been provided to employers to ensure they had all the information they needed about their obligations.
Vaughan said employers could face consequences if they did not observe the rules, and foreign workers should also abide by the laws.
"Any employer who exploits individual employees is actually committing an offence against the Immigration Act, which carries a significant penalty of seven years' imprisonment or a fine not exceeding $100,000, or both," he said.
"The first thing is that employers have certain obligations when employing migrant labour and also migrant workers have a responsibility to ensure that they remain lawful while they're in New Zealand and working, so there are clear messages for both employers and employees."
RNZ has approached the Chinese consulate for comments.