Immigration New Zealand says officials have tracked down some of the Tongan nationals who were in New Zealand with undeclared criminal records.
Last month the police in Tonga identified 172 cases where officers cleared criminal records for people applying to come to New Zealand.
Immigration says about 50 are thought to still be in New Zealand.
Its national manager for compliance operations, Dean Blakemore, says two people have been deported to Tonga and one has returned voluntarily so far.
"The majority of the people who are here in New Zealand on these sanitised or cleansed police certificates are at the lower end of the scale in terms of offending. There are some who are not but a majority of them are not, so people should not be concerned"
Dean Blakemore says some of those are now permanent residents, and 12 have been overstayers.