Another 10,000 pieces of undelivered mail have been discovered by Queenstown police.
The mail was found in a room at a storage company in Manse Rd, Arrowtown, bringing the number of items discovered so far to more than 20,000.
A 32-year-old postie, who lives in Frankton with other flatmates, was arrested on Friday after New Zealand Post reported its suspicions over undelivered mail.
Since Wednesday, police and NZ Post staff have been counting the undelivered mail to re-issue to the rightful owners next week.
Among the mail was an envelope addressed to the woman's old Fernhill address from the storage company. This led police to find a further estimated 10,000 items in the Arrowtown storage room.
New Zealand Post would be examining its processes in order to prevent a recurrence and regain the public's confidence, as complaints from Fernhill residents over lost mail dated back more than a year.
The company was not "shirking accountability and we're going to do a very thorough appraisal of our systems".
Police confirmed some of the mail had been opened and they would be making inquiries with those senders and recipients who could be identified to ascertain whether any property had been removed.
The woman is to appear in the Queenstown District Court on one charge of theft by person in a special relationship.