Women at an Auckland prison have been routinely confined to their cells for periods of up to 29 hours at a stretch - well outside a law which says they should get at least one hour out of their cells a day.
RNZ took evidence of the lockdown hours, including one prisoner's diary, to the Corrections Department, which has now launched an urgent review and pledged to stop it happening again.
The action comes after weeks of denial from the department and its Minister Kelvin Davis that the excessive lockdown hours were happening at all.
RNZ's Investigative journalist Guyon Espiner reports.