Countdown's Dunedin South store has been closed for more than two weeks due to the rat problem. More than 20 of the rodents have been captured since February 10.
The store was due to reopen today, but Woolworths New Zealand director of stores Jason Stockhill said that was now on hold.
"Rentokil reported a rodent gained entry to the store overnight, triggering a camera sighting."
He said the issue was being discussed with the Ministry for Primary Industries.
The company would provide an update on reopening when it could, he said.
New Zealand Food Safety previously said its investigation into the cause and scale of the problem 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."
