Investigation into rat-plagued Dunedin supermarket could take months

A rat-plagued Dunedin supermarket will not reopen until Thursday at the earliest.

The Ministry for Primary Industries is investigating after more than 20 rats were caught in Countdown Dunedin South since its parent, Woolworths, closed the store earlier this month for pest elimination.

New Zealand Food Safety deputy director-general Vincent Arbuckle said the investigation might take months.

"People rightly expect high levels of hygiene at supermarkets and to that end we continue to step through our investigation," he said.

"Such investigations must be done thoroughly to ensure we understand the causes and scale of the problem so that it can be prevented from recurring.

"As with all investigations we keep an open mind and follow the evidence, so we are unable to put a definitive time frame on it. However, given the complexity and need for thoroughness, we consider it could take months. We are unable to go into detail about these ongoing investigations, but understand people are interested in this matter and will continue sharing information where we can."

The store remained closed at present.

"Countdown Dunedin South will remain closed until both New Zealand Food Safety and Woolworths are satisfied the additional pest-control measures have worked," Arbuckle said.

"To help guide that decision, we have put in place a 48-hour period to allow monitoring to determine if the measures have worked. This 48-hour period will start once we have evidence that there has been no rodent activity for 24 hours. We will continue to monitor the store after it reopens to ensure its pest management is effective.

"In addition, a review of Woolworths' pest control and maintenance practices in its New Zealand operation will be undertaken by a third-party verifier appointed under the Food Act 2014."

A Woolworths spokesperson confirmed another rat had been caught at the store overnight.

"The earliest the store will open at this stage is Thursday."