Food safety officials have stopped a third North Island egg producer from selling eggs after tests found a strain of the potentially dangerous bacteria salmonella.
Hens or eggs cannot be moved off the property after the farm tested positive. Salmonella can cause diarrhoea, vomiting and fever, and can be particularly serious for the elderly, frail, and pregnant women.
New Zealand Food Safety has been carrying out tracing and testing of poultry operations after salmonella was found at an Auckland hatchery earlier this year.
Last month, NZ Food Safety stopped two farms from selling eggs after tests found salmonella.
Eggs that could be of concern are marketed under multiple brand names.
NZ Food Safety director of food regulation Dr Paul Dansted told Checkpoint no eggs have tested positive but the agency is being cautious.
The ban will stay in place until officials are sure the eggs are safe.
"The chickens on this farm are layer hens, so they're producing eggs. At the end of their life they may go into the meat chain, or they might go into pet food or other avenues, but our real interest at this point in time is stopping the eggs moving on [and] making sure if they were infected hens they wouldn't go on to another farm and infect another farm," Dr Dansted said.
"We've done lots of testing of eggs and we haven't found any of the salmonella in eggs, but our concern is that it's possible it could be there and it can actually grow and multiply in people homes, so we're recommending that people refrigerate their eggs at home and cook them thoroughly.
"There have been eggs moving from this farm before the notice. They tend to move through the supply chain pretty quickly. So while there won't be any in the supply chain, it is possible that there are some of these eggs in people's homes.
"So what we're recommending is cook your eggs, refrigerate them if you've got them in the home, but also pay attention to the date marking. Don't keep eggs beyond their expiry.
"If there is a farmer or a product that's readily identifiable, you've got a particular brand or a particular date, that kind of information we can and will provide to consumers and we've got a list of those sorts of things on our website right now.
"In this particular case, the product isn't identified from this particular farm, so it's not particularly helpful information."
Dr Dansted said the farm supplies a number of brands, but he could not say how many.
"While we haven't found it in a widespread sense , our concern is that it could potentially be out there. So we're putting controls on farms… sampling and testing and movement controls as well.
"A couple of weeks ago we issued notices of directions on two other farms and that's already been reported publicly."
The farms under scrutiny are not owned by the same people, but all operate independently, he said.
"We initially had traced back product in March this year to one hatchery in Auckland… we've been tracing forward and that's how we've found these other farms.
"All the properties we've found so far we can trace back to the hatchery in North Auckland.
"Our working assumption is that the hatchery in Auckland has had an infection and those birds have moved to a number of different farms, and that's moved through the supply chain.
"When we first traced back to the hatchery in Auckland, we traced forward to a total of 64 farms. There were 18 of those that were high risk because they were in the risk period, weren't doing sampling and testing of their own and were linked back to potentially infected flocks.
"So of those 18, we've put additional sampling and testing in place. As a result of that sampling and testing, we put movement controls on two of them.
"It does seem to be relatively well contained, but we're going to continue investigating this. We're going to continue looking broader, but at this point in time there are three farms under control."