The Ministry of Primary Industries is investigating a video showing a mouse running across uncovered salad in a Christchurch supermarket deli.
It follows a months-long fight to remove rats from a South Dunedin supermarket.
New Zealand Food Safety deputy director-general Vincent Arbuckle said he was alerted to the video at Christchurch's Eastgate Countdown on Sunday night.
"Totally agree that that is not consistent with good hygiene and good food safety practice to have a rodent like that around food, which is ready to eat," he said.
"Completely inappropriate."
He confirmed Woolworths was investigating the incident including what was done.
Countdown's owner Woolworths director of stores Jason Stockill said the incident was reported last Wednesday and its pest control contractors identified and sealed some entry points into the store.
"A dead mouse was found the next day, indicating our pest control programme is working and there have been no sightings since," he said.
"We would like to apologise to our customers for this incident and reassure them that food safety remains a focus for us."
A senior Food Safety officer was onsite on Monday to see whether there was any evidence of this being a systemic issue.
Arbuckle said it was believed to be an isolated incident, but they were waiting for a report from Woolworths to find out more details.
Stockill said they also believed this was an isolated incident, and were reviewing their pest management control programme for the store alongside Rentokil - a pest control service.
"Our store team work hard every day to maintain our high standards for cleanliness and work closely with pest control services to manage rodent populations that can be found in urban areas."
Arbuckle said the protocol should be clear - remove and destroy any contaminated food and track down the mouse.
"There's no place for ready to eat food and vermin."
The video is understood to have been taken earlier this month.
He confirmed there have been no other reports of vermin at the Eastgate supermarket.