All of the samples of infant formula tested by police after being suspected of possible tampering have tested negative for 1080.

Authorities are no closer to saying if the threat to poison baby formula with 1080 was a hoax, or who wrote the blackmail threats - even with 30 staff on the case.

Police are testing infant formula after a number of tins were found with pin-pricks in packaging lids.

Dairy companies are confident security measures at their facilities are tight enough to prevent a 1080 contamination.