Photo: Flickr / David Zoppo
The prison watchdog expects to finish visiting all 18 of the country's jails before the end of the month.
The Office of the Inspectorate is investigating how people under 25 are being treated in custody.
It said inspectors visited just under half of New Zealand's prisons between mid-January and the end of last month and have spoken to more than 70 young men and women who have been remanded in custody, or sentenced to jail.
The inspectorate expects to finish the visits by 20 March and publish the report mid-year.
The inspections, which began in September, will assess whether Corrections is acting in line with New Zealand law and international best practice.