Retailers are moving to reassure customers they are doing everything they can to boost security in their stores.
Infant formula retailers around the country have ramped up their security in the wake of the threat to put 1080 in formula supplies.
A staff member was monitoring the infant formula area at New World Ilam in the western suburbs of Christchurch today.
The shelves were cordoned by red-and-white tape and information leaflets and signs were highly visible.
"For you and your families' health and safety, infant formula sold in this store is now under increased monitoring," said one sign.
Shoppers were limited to two tins each.
The shop 'milk monitor' stopped a NZME. News Service reporter from taking a photo of the area today.
The store manager said that the milk monitor would be keeping a close eye on the area at all times.
High-definition close circuit security cameras were also trained on the shelves. The store manager said parents seemed satisfied with the increased security and had not expressed any concerns to him.
An information sheet at the store advised customers to check packaging for signs of tampering before buying or using it, and not to purchase the products if there were any doubts.
It also encouraged shoppers to report an unusual or suspicious behaviour in store.
The information sheet also had contact details for government's Food Protection website, police, Healthline, and Plunket.
Nearby Pak'nSave Riccarton, part of the same Foodstuffs group, had decided to remove its infant formula from the shelves.
They are now being kept in a "secure location" with 24-hour CCTV surveillance.
"All infant formula can be purchased at checkout through your checkout operator," a sign said.
Countdown Upper Riccarton had also removed the formula from its shelves.
It was being kept behind the customer service counter.
Shoppers were advised to ask staff for assistance in buying it.
One Countdown shopper and mother approached outside the Upper Riccarton supermarket was satisfied with the increased security measures.
"I was pretty concerned about it when I heard about the threats yesterday, but seeing how seriously they are taking it, and given that the cans are pretty well sealed, I'm confident that everything is ok," said the woman, who asked not to be named.
The Warehouse is actively working with the Ministry for Primary Industries on the infant formula contamination threat, it says in an email to customers.
The email notified customers that significant additional security measures had been put in place throughout The Warehouse's distribution chain.
These included additional security processes, as well as checks and monitoring, in all of The Warehouse's distribution centres and stores.
All infant formula had been removed from the shelves of The Warehouse's 92 stores nationwide and could now be purchased in-store from the customer service counter.
CCTV cameras would remain on the product at all times while in storage and when behind the counter.
Random sampling of infant formula product would also be undertaken, in conjunction with MPI.
The Warehouse apologised to customers for the extra time it may take for customers to purchase infant formula, but said "customer safety is our absolute priority and we are supporting the police and MPI in any way we can".
Foodstuffs also issued a media release reassuring customers that it had an "important role" to play in keeping customer confidence.
"Across our Foodstuffs stores of New World, PAK'nSAVE and Four Square we are committed to ensuring parents and caregivers can continue to access their normal range of infant formula," Foodstuffs managing director Steve Anderson said.
"We have implemented a number of additional security protocols through our supply chain and in-store to give customers confidence in the infant formula purchased from our stores. Our approach is essentially to 'bring security to the shelf'."
Meanwhile, the reaction of countries to the 1080 contamination threat is evidence that the Government's response was correct, Prime Minister John Key says.
Mr Key said the major overseas market of China had set some conditions on the importation of infant and other formula from New Zealand - but its borders remained open.
"They are responding to the fact we have been open with them, engaged with them, and they are confident in our testing process, so that is good news.
"All we are simply saying to them is, look, we'll give you the tests as well. They have set a few conditions, we are meeting those, and that means the borders stay open in China."
Asked about international advice that the threat - likely considered a hoax by police - should not have been made public, Mr Key defended the announcement.
"The decision yesterday was recommended by officials because of media enquiries...but the overall decision though to go public [later this month] was made by myself and a senior group of ministers a long time ago."
Mr Key said that was because he believed the Government "owe it to consumers to say, look just be a little bit more vigilant". Not going public would be perceived as a "cover-up", he said.
Earlier, Mr Key defended the Government's decision to keep the 1080 contamination threat secret until yesterday.
The threat to infant formula was revealed to the public yesterday because "chatter about it in Auckland" had led to several journalists being tipped off, Mr Key said.
"We always knew there was a risk that it was going to break, I mean, over 1000 people knew," Mr Key told Radio New Zealand today.
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Mr Key said the police did not want the threat made public as it could have compromised the investigation.
A reliable test for 1080 contamination also had to be developed.
"There was no test for 1080 because it's not a substance you would find in milk powder, so one had to be created and then the robustness of that tested."
Mr Key told Radio New Zealand the manufacturing process also had to be reviewed.
"And of course the threat in the letter said that we had until the end of March to change our use of 1080."
Meanwhile, police investigating the 1080 threat have appealed for the person responsible to "do the right thing" and come forward.
At a conference at Police National Headquarters this morning, Deputy Commissioner Mike Clement said the police investigation was progressing well.
"We are very encouraged with the response we have had from the public.
"It's most likely with the public's help this matter will be brought to a conclusion."
He asked the person involved to "do the right thing" and make contact with police to prevent further "fear for mums and dads".
"We want to hear from you so we can get this matter resolved."
Mr Clement said police had "many persons of interest" in the investigation, but would not comment on who police had interviewed.
More leads were expected now the information had been made public.
"I think the public will solve this as they often do in serious investigations."
He said any previous threats indications and attitudes in relation to 1080 were of interest to police.
Mr Clement said all "pros and cons" were considered when deciding whether or not to notify the public of the threat.
The decision was reached across all of the agencies and government -- no one drove the decision. "It was better to be open and transparent than to withhold it."
Mr Clement said it was always the intention to go public with the threat.
He confirmed the letters came through a New Zealand postal centre, but would not comment on whether police had formally interviewed anyone as a suspect.
Dr Pat Tuohy, chief advisor from the Ministry of Health, told the press conference he appreciated parents were feeling "anxious and angry".
"They can reassure themselves about the safety of the infant formula chain."
Formula was as safe today as it was before the threat was made.
Concerned parents could check products for tampering, he said. "It's not hard to do and can make them feel a lot safer about the formula they are feeding their babies."
He encouraged parents not to change from the formula they were using.
Mr Tuohy recommended any parents with ongoing concerns to do as they normally do and seek advice from a health practitioner, such as Healthline, Plunket or their family doctor.
He said it would it would only take a very small dose to be lethal for a baby.
He said 1080 was not discernible by taste or colour. This would make it more difficult to detect. However, he continued to assure parents that the likelihood of any poison making its way into infant formula was "tiny".
Food Safety Minister Jo Goodhew said the testing regime did not start until late January because laboratories needed to be geared up with equipment and capabilities to carry out the work.
"We tested the product that we already had on hand, both MPI and Fonterra product, and then as the other manufacturers were contacted we were able to uptake testing all of their products as well," Ms Goodhew told Radio New Zealand.
A total of 45,000 samples had now been tested, including every batch of infant and other formula, and raw milk.
"We're looking at detection to one part per billion of 1080 pesticide, we're testing to that level and we can tell you we've found absolutely nothing across 45,000 samples."
Product samples dating back to September had also been checked, and extra security measures put into the transport and delivery chain.
Ms Goodhew said testing would continue for as long as necessary.
"Health and wellbeing of the consumer is at the forefront of everything we're doing."
Food and Grocery Council chief executive Katherine Rich said she was briefed by the Ministry for Primary Industries in mid-February, and given background on what had occurred and the mitigation steps taken.
However, she told Radio New Zealand she signed a confidentiality agreement so was not able to tell anyone.
Her first move was to check policies on malicious product tampering.
"Most of our member companies deal with these sorts of incidents and plan for these incidents."
Ms Rich said supermarkets were notified the following week "and immediately kicked into gear".
"Since that time a lot of planning has been put into place ... and I think all of us are very confident that we've had the time to put a number of additional procedures in place, so we can look particularly mothers in the eye, and say your product is safe."
Ms Rich said security was so high at dairy plants that one company CEO had told her he was unable to get through security at his own factory unless carrying the right credentials.
Ms Rich said the extra security measures and testing were costly and complex.
"That's why there's a lot of anger within the industry because this person has already cost the economy millions of dollars."
Ministry for Primary Industries deputy director Scott Gallacher said all infant formula had undergone a "comprehensive batch testing regime" - from raw milk through to the finished product.
The size of the batch depended on a variety of factors.
"The testing is just one part of the overall security we have across the whole manufacturing and supply chain.
"At each point we have increased vigilance," he said.
Mr Gallacher said they were providing the same information to overseas markets as they were to New Zealand consumers.
He said MPI appreciated how markets had responded in a "calm" manner.
"All the markets we are talking to and engaging with are still allowing the product through," he said.
Mr Gallacher said the public could be assured comprehensive measures were in place to ensure there was no risk to consumers.
"On top of our already quite strong and comprehensive testing regime, which we already have in play ... we have put in place additional 1080 testing.
"That has now almost ticked over 45,000 tests."
The tests were occurring at "key points" throughout the supply chain, he said.
This would give mums, dads and consumers "the confidence and assurance" that there was no 1080 in any parts of the supply chain.
He said the testing included formula dating back to September last year - prior to the threat.
"We have been testing through historic samples, and it's also now in real time -- each day we are doing further testing and it is all negative."
Testing was just one part of the puzzle. "The other important part is all of the security mitigations the manufacturers and retailers have put in place to make sure they have complete control of the product.
"The testing is just one part of the overall security we have."
He said MPI was releasing videos to the public and information on all the key checks and balances occurring in the manufacturing process.
Chris Claridge, managing director of infant formula company Carrickmore Nutrition, said the Government's response was "unusual" and would not be considered international best practice.
He told Radio New Zealand threats against food safety were "fairly standard" for international food companies, and in general where contamination has not occurred, the public would not be alerted.
"What we are seeing here is a government response that is unusual and it would not be considered international best practice to respond in this manner," he said.
"What we see internationally is generally they don't carry out the threats, they are a mechanism to gain publicity.
"But what this does now is sets a precedent for how the government will react in the future, because these food threats will keep occurring."
Mr Claridge said the testing regime was costing $300 per test.
With 45,000 tested samples, that would mean the Government had so far spent $13.5 million on testing alone.
Comment was being sought from MPI on the cost of the testing regime so far.
Late November:
• Fonterra receives a threat posted to its Wellington office, addressed to the chief executive Graham Smith, containing samples of formula contaminated with 1080.
• A similar letter and sample is sent to Federated Farmers chief executive Graham Smith at the organisation's Wellington offices.
• The threat is reported immediately to police.
• Prime Minister John Key is told soon afterwards.
• Police launch Operation Concord in Auckland, involving up to 36 staff. The Ministry for Primary Industries (MPI) and other agencies are brought in to help with the operation.
Late January:
• Testing of product samples begins.
Mid February:
• Food and Grocery council chief executive Katherine Rich is briefed by MPI.
Late February:
• Supermarket chains are notified of the threat.
Tuesday, March 10:
• NZX halts trading on three listed dairy companies and all dairy futures.
• Police announce publicly that a threat has been made to contaminate infant formula with 1080.
Wednesday, March 11:
• John Key reveals the threat was made public because information had already reached members of the media.
• Food safety minister Jo Goodhew says 45,000 formula samples have been tested, with none found to be contaminated.
March 31:
• The deadline for the blackmailer's demand to end use of 1080.
One adult died at the scene and three people suffered minor to moderate injuries.