An investigation into the possible exploitation of international students by private training schools could take several more months.
Immigration New Zealand says it is looking into the activities of up to 25 schools.
A fraud manager, Peter Elms, says investigators believe some private training establishments are bringing students to New Zealand intending to put them into jobs where they are paid well below the minimum wage and are made to work for more hours than their visas allow.
Possible penalties include suspending the processing of student visas, deregistering schools, and up to seven years in prison if false and misleading information has been provided to Immigration New Zealand.
Mr Elms says labour inspectors and the Qualifications Authority are helping with the investigation, which began in June.