The migrants were promised jobs with a handful of employers who are now being investigated over the mistreatment claims.
Investigators have been to the residences where the workers were staying and found that these properties were unsuitable for accommodating such a large number of people.
Immigration NZ said it was working with the Indian High Commission in New Zealand and the Bangladeshi High Commission in Australia during its investigation.
Victim Support, the Ministry of Social Development and the police as well as community representatives were all helping with the migrants’ welfare.
In the meantime, Immigration said it was also speaking to all the migrants and expected this would take some time. The migrants were also being encouraged to attend MSD’s Jobs and Skills hubs.
Immigration NZ said it has finished a review of 190 people overseas who also got the visas, and who were linked to the companies under investigation.
It said 135 of those people have had their visas cancelled.
Of the remainder, some people have applied for a new visa, some visas have expired and a few have been cancelled at the border.