A rat-plagued Dunedin supermarket has pushed back its reopening again after another rat sighting.
Countdown Dunedin South has been closed for almost two weeks to eliminate the pests after the issue was first discovered late last year.
There have been 22 rats captured since 10 February.
On Wednesday, the supermarket confirmed it was working towards reopening on Saturday after another rat was spotted on Wednesday.
New Zealand Food Safety is investigating the cause and scale of the problem, saying it could take several months.
Deputy director-general Vincent Arbuckle said the complexity and need for thoroughness meant it would take time to investigate, so it could be prevented from happening again.
"We are satisfied Woolworths is taking the matter seriously and is putting in place all the right measures at the store to manage the problem, including deep cleaning, maintenance and proactive pest control measures," Arbuckle said.
"Given the very high level of public interest, we want to see a 24-hour period of no rodent activity, followed by a 48-hour period to determine if the measures have worked before reopening.
"Following reopening, our food compliance officers will monitor the store for a period so that consumers can have confidence food at the store is safe."
Woolworths' pest control and maintenance practices in New Zealand are under review by a third-party appointed under the Food Act 2014.