A New Zealand-made product exported to China is the latest food item found to contain the industrial chemical melamine.
The Food Safety Authority will not name the product, which is also available in New Zealand, until its tests are completed.
On Wednesday, the authority issued an alert over the Chinese-imported sweet White Rabbit Creamy Candies, which have been found to have unacceptably high levels of the toxic chemical.
The authority is investigating the second tainted product after Chinese importers found melamine during independent testing.
It has not yet issued a recall and says it needs to establish that the product is a risk before publicly naming it.
The authority says any number of companies in New Zealand could have made a product containing melamine, and minute amounts of it are present in many products.
FSA compliance director Geoff Allen says the chemical may have leached from plastic involved in the product's packaging or processing. However, he says this does not present a health risk to consumers, because of the low levels of melamine involved.
The authority hopes to complete an investigation by the weekend.
Food Safety Minister Lianne Dalziel says the detected levels are minute and it is unlikely that the toxin was added intentionally.
However, Green Party's food safety spokesperson Sue Kedgley says the public has a right to know immediately which products are being tested.
Chinese sweets not recalled
Ms Dalziel on Thursday defended a decision not to recall melamine-tainted sweets imported to New Zealand from China.
She says the Food Safety Authority issued a Director-General's Statement which is intended to inform the general public, not just retailers.
Ms Dalziel says there is a misconception that recall notices are the best option, but in cases in which multiple importers are involved, it can be less effective.
Ms Kedgley says a recall is the quickest way to solve a food safety issue such as this.