Police have been contacting known 1080 opponents in a bid to find the person behind a threat to contaminate New Zealand's baby formula stocks.
While police would not say who they were speaking to, Ban1080 party candidate Tricia Cheel confirmed detectives had visited her on Tuesday night soon after the investigation was made public.
"I guess they were just following up and wanted to check whether I knew anybody that may be capable of doing such a thing," she said.
"I was surprised. I felt that surely they were looking in the wrong place. It was a knee jerk reaction... they were barking up the wrong tree."
Ms Cheel said she had been campaigning for 25 years to get the government to stop dropping 1080 in New Zealand.
She described the practice as a form of "eco-terrorism against the community".
"Using 1080 is a terror act against the people of New Zealand. This is what we're fighting, so why on earth would we go and do something like this? We are the last people that should be considered," she told the Herald.
"I just hope they get to the bottom of this. What a thing to do - to threaten the most vulnerable members of society."
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Security has been ramped up at supermarkets and laboratories after the threat was made to contaminate infant formula with 1080.
Environment Minister Nick Smith said current controls on 1080 poison were "robust", but had been ramped up after the public learned threatening letters containing lethal doses of 1080 were sent to Fonterra and Federated Farmers in November.
Dr Smith said "additional controls" would be enforced in laboratories.
The anonymous letters stated formula would be contaminated with 1080 if New Zealand didn't stop using the poison by the end of this month.
Current laws had an exemption for research laboratory use, as was the case for dozens of similarly toxic substances, Dr Smith said.
Dr Smith said the Government had discussed the tighter security with research laboratories, and the Governor-General signed off the new regulations last night.
The quantity of the poison that was being stored and used would be tracked and importers would need to obtain an Environmental Protection Authority certificate.
"These regulatory changes make it unlawful for anybody to possess 1080 without the prior approval of the Environmental Protection Authority, including research laboratories.
"It will enable the Authority to better track the importation, distribution and use of high purity 1080, and ensure it is always securely contained," Dr Smith said.
Prime Minister John Key said China had kept its borders open to New Zealand, but set some conditions on the importation of infant and other formula.
He defended the move to make the threat public.
"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.
Food and Grocery Council chief executive Katherine Rich said she was briefed by the Ministry for Primary Industries (MPI) in mid-February, and supermarkets "immediately kicked into gear".
implemented 'milk monitors', staff who watched infant formula and could give customers MPI advice, additional CCTV cameras and signage in all supermarkets.
All infant formula had been removed from the shelves of The Warehouse's 92 stores nationwide and could be purchased from the customer service counter. CCTV cameras would remain on the product at all times while in storage and when behind the counter.
Meanwhile, Deputy Commission Mike Clement said police had "many persons of interest" in the investigation in to who was responsible for making the threats.
He would not comment on who police had interviewed as part of the investigation, but said police expected to gain more leads now the information had been made public.
How the formula threat unfolded
• 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.
• Testing of product samples begins.
• Food and Grocery council chief executive Katherine Rich is briefed by MPI.
• 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.
• The deadline for the blackmailer's demand to end use of 1080.