Woolworths Dunedin South (formerly known as Countdown Dunedin South) was closed for 18 days in February after numerous sightings and captures of rodents in-store.
It reopened on February 28, but Woolworths New Zealand director of stores Jason Stockill said a "small number" of rats had been captured since the store reopened five weeks ago.
The New Zealand Herald reported two more rats had been caught.
NZ Food Safety says given the size and nature of supermarkets, rodents can get inside from time to time and, generally, stores did not need to close each time as long as it was dealt with promptly and in a way that minimised food safety risk.
Mr Stockill said the captures showed the store’s pest management plan and processes were working as they should.
"Pest management is a critical part of operating a food business and we take our responsibilities in this space very seriously.
"We're continuing to work closely with (pest control company) Rentokil and New Zealand Food Safety across the country."
First Union organiser Angus Wilson said the situation had died down, but there were now "rumours that rats had returned".
"I think communication has improved, but there’s a still long way to go in distributing information to all of the staff.
"I would certainly be hoping that if there are more sightings that management would be upfront with staff."
Twenty-three rats were caught while the store was closed to focus on targeting the problem.
A staff member told the Otago Daily Times yesterday that although the situation was not as bad as it was "also really hard to know because the information isn't being shared with general staff".
"We're still being kept somewhat in the dark. It’s been mixed."
NZ Food Safety deputy director-general Vincent Arbuckle said they were satisfied Woolworths had "maintained its focus on pest management since the store reopened".
"We don’t have a specific number of rats that would trigger further action, such as closure.
"Rather, we make assessments based on several factors taken together, including number of rats captured, sightings on CCTV footage, and evidence of rat activity, any direct impact on food safety, and whether standard pest management tools are generally managing the problem."
He said food compliance officers were continuing to visit the store periodically and Food Safety received regular updates from Woolworths so consumers could have confidence food at the store was safe.
University of Otago public health Professor Nick Wilson said there were aspirations to make cities "rodent free" as part of the goal of Predator Free 2050.
"There are technologies being developed that in theory could over time eliminate rats, but at a practical level in modern cities, it is possible to have very intensive pest control that basically eliminates rats.
"Indeed, the suburb of Miramar in Wellington seems to have succeeded in eliminating rats — by using extensive trapping.
"Another example, is the entire Canadian province of Alberta which has been able to stop rats coming in — and when they do get through, they have conducted pest control that eliminates them again."
He said rats could only get in structures such as supermarkets if there were not proper preventive measures in place.
"There is really no excuse for rats being in supermarkets — it is an unacceptable system failure if this happens."
