A massive response prompted by the recent 1080 milk formula threat included ensuring hospitals could test for the poison in cases of sudden infant death.

Various government agencies have this afternoon released heavily-redacted documents outlining the wide-ranging response to the threat.

Anonymous letters sent to Fonterra and Federated Farmers in November said formula would be laced with 1080 if New Zealand didn't stop using the poison for pest control by the end of March.

Police launched operation Concord in response. No arrests have been made.

Advertisement

A Ministry of Primary Industries document from February outlined how the health sector was preparing to respond to the threat.

"MOH [Ministry of Health] advises that sudden infant deaths (SIDs) occur once or twice a week in New Zealand from varied and sometimes unknown causes," the document stated.

"After the threat is publicised, it is possible that unexplained infant deaths may be attributed to 1080 poisoning. MOH is working with MPI to ensure that hospitals have access to 1080 testing procedures that would confirm or rule out the possible involvement of 1080 in a SID."

Police have visited more than 3500 dairies, supermarkets, pharmacies and service stations to discuss issues including how to safeguard formula from tampering.

Hundreds of thousands of pamphlets have been distributed, regulations around the use of 1080 strengthened, and there has been extensive testing of products.

The documents show several communication plans were drawn-up - one in the case that news of the threat was suddenly made public, and another if a media request was received that was vague enough to suggest there was time to plan an announcement.

There was also contingency if the news came out over the Christmas period. It was eventually announced at a media conference in March, after previous media enquiries.

Timeline of a threat

• November 27, 2014: Fonterra and Federated Farmers receive a letter threatening to contaminate infant formula.

• On the same day a watch group of government agencies is formed to consider the threat. The Prime Minister, the Minister for Primary Industries, the Minister for Food Safety, the Minister of Police, the Minister of Foreign Affairs, and the Minister for Trade.

• January 15, 2015: Milk testing methods validated, and the sampling strategy approved.

• February 10: First meetings with affected infant and other formula manufacturers.

• February 11: Initial meetings with major global suppliers.

• February 13: Food and Grocery Council chief executive told of the threat.

• February 18: Initial meetings with New Zealand supermarket chains.

• February 25: Labour leader Andrew Little told of threat.

• March 10: Public announcement at media conference.