Suspected 'eco-terrorists' have threatened to poison baby formula in New Zealand unless authorities ban a particular agricultural pesticide.
Anonymous letters have been sent to a national farmers' group and to Fonterra, the world's largest dairy exporter, containing samples of infant formula laced with the poison known as 1080.
The letters, which are being treated as blackmail, threatened to contaminate more formula unless use of the poison, a pesticide, ceased by the end of March.
Police in the country suspect activists opposed to the use of the pest control could be behind the threat - and despite considering the possibility it could be a hoax, they have carried out more than 40,000 tests on products so far, with none showing any trace of 1080.
Parents have been warned to stay vigilant for any signs their formula may have been tampered with, while security at shops and manufacturing and packaging plants has been stepped up.
Prime Minister John Key and Minister for Primary Industries Nathan Guy have both condemned the letters as "eco-terrorism".
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.
A trading halt has now been placed on shares in Fonterra, as well as smaller dairy firms A2 Milk and Synlait Milk.