Fonterra chief executive Theo Spierings and Tatua chief executive Paul McGilvary said everything possible was being done to lock down the supply chain since criminal threats of blackmail were received in late November.
Those threats by letter to Spierings and Federated Farmers head office, including sachets of 1080, were immediately passed to Police and government officials advised.
“This is blackmail against New Zealand and the dairy industry won’t tolerate it,” McGilvary said.
No more threats had been received since and more than 35,000 additional tests specifically for traces of 1080 had not detected any.
Before the threats milk and infant formulas were not routinely tested for 1080.
The letters threatened to contaminate infant formula and other products if NZ did not cease using the poison in the environment by the end of March. It also threatened to disclose the matter publicly.
The Police have said the threat is probably a hoax but had to be taken seriously.