Police are appealing for the publics' help following a threat to contaminate infant formula and other formula in an apparent protest over the use of 1080 poison in pest control.
Federated Farmers and Fonterra received anonymous letters in November. Small packages of milk powder, which later tested positive for a concentrated form of 1080, accompanied the letters.
The letters carried a threat to contaminate formula with 1080 unless New Zealand stopped using the poison for pest control by the end of March.
Police said the letter was likely to be a hoax, but the person or people who wrote the letters threatened to make their threat public if the Government did not meet their demand by the end of this month.
Prime Minister John Key said it was a "form of ecoterrorism, without doubt".
That was despite officials being very confident the risk of the threat being carried out was low.
He said he was confident every measure had been taken to address the threat. He was very confident New Zealand's food remained safe.
Speaking at a press conference at Parliament, Mr Key said his message to parents was that there was a low likelihood of the threats been acted upon, and he was confident that food products were safe.
Minister for Primary Industries Nathan Guy said since the threats more than 40,000 tests had been carried out on products and no infant or other milk formula product had shown any trace of 1080.
"Police have advised there is a low likelihood of the threat being carried out, but because of the nature of it, both the police and ministers have taken the treat seriously," Mr Key said.
"I want to reassure parents that every step possible has been taken to respond to the threat, to ensure the ongoing safety of our food products.
"Obviously we also needed to work with the industry to ensure every step was taken to protect the supply chain before the public was informed," Mr Key said.
"These steps include the development and implementation of a specific testing regime. Official advice was to be very cautious about making this threat public until appropriate measures were in place. Today there have been a number of media queries so we have brought the announcement forward."
"Police have advised there is a low likelihood of the threat being carried out, but because of the nature of it, both the police and ministers have taken the treat seriously," Mr Key said.
"I want to reassure parents that every step possible has been taken to respond to the threat, to ensure the ongoing safety of our food products."
"It is eco-terrorism," Mr Guy said this afternoon. Mr Guy said the criminal blackmail threat was "absolutely appalling."
He said 40,000 tests were carried out in recent weeks and 20 manufacturers contacted.
No traces of 1080 were found in any of the tested products, Mr Guy said
Police National Headquarters said a full investigation began in November, with an Auckland-based team called Operation Concord involving up to 36 police staff.
Mike Clement, Police deputy commissioner of national operations, said although it was possible the threat was a hoax, it must be treated seriously. He encouraged the person or group to make themselves known.
"The letter writer may not have really considered the implications of their actions when this communication was drafted," Mr Clement said.
Several specialist groups and support agencies, including MPI, were involved.
Federated Farmers was also helping with the investigation.
Mr Clement said authorities were using all available resources to resolve the issue but wanted the public's help.
"You might be aware of someone who has strong views [about] 1080 and has made threats," Mr Clement said. "Please make contact with us."
"This criminal threat is designed to cause fear in order to generate a domestic policy outcome," Ministry for Primary Industries deputy director general Scott Gallagher said.
People should check packaging for any signs of tampering as a result of "this criminal blackmail threat", even though Mr Gallagher said formula was probably actually safer now than ever before, thanks to enhanced safety regimes.
Mr Clement said police treated the incident as a "crime of blackmail" rather than a terrorist act.
No particular brand or company's formula was targeted.
Mr Clement said the investigation commenced in secret but it was time to ask for the public's help, and police also believed the threat was low, so there was no need to go public before.
He said police had always treated the case "very seriously" despite starting inquiries out of the public eye.
"There are many other factors to consider, one of which has been food safety."
He said trading partners and some customers had been informed at an earlier date, but the potential for financial loss was not at the forefront for the company.
Mr McGilvary supported that sentiment.
"We have to protect people... We are conscious that we want to keep markets open and keep doing business."
When asked why the dairy industry hadn't informed the public, the representatives said it was down to police and government investigations while the industry focused on safety and security.