China blocked 42 tons of Fonterra's whole milk powder from entering the country in May after checks at the border found excess levels of nitrites and it was sent back to New Zealand, the scandal-hit dairy giant confirmed Thursday.
Earlier this month, the world's biggest dairy exporter said it had found bacteria that could cause food poisoning in whey protein concentrate.
Fonterra said the milk powder was tested before leaving New Zealand and met specifications. "It was then shipped to China, where local tests showed it no longer met specifications."
Nitrites occur naturally in water, soil and food and can be used as fertilizers and preservatives.
Excessively high levels can be toxic.
Fonterra's group director of food safety and quality, Ian Palliser, said that the milk powder showed nitrite levels of between 1.4 parts per million and 1.8 ppm when it was shipped from New Zealand, but showed higher levels in Chinese tests, Reuters reported.
"The limit is 2 parts per million in China and the product tested at somewhere between 2.4 ppm and 2.8 ppm," Palliser told Radio New Zealand.
He added that China had a much lower threshold for nitrite levels than New Zealand, where levels of up to 5 ppm are considered safe for domestic consumption. Palliser said that the levels were "not a food safety issue whatsoever."
China's General Administration of Quality Supervision, Inspection and Quarantine said two batches of Fonterra's milk powder were imported by two Shanghai trading companies but didn't specify the amount of nitrites involved.
The troubled dairy giant pledged to step up quality checks at its plants.
It was revealed on Wednesday in New Zealand that a shipment of Fonterra-made lactoferrin was also stopped in China in May after Chinese authorities found it contained excessive levels of nitrates.
Fonterra said it launched a program that would provide additional quality assurance for its nutritional plants.
The dairy company reported earlier this month that some of its exported whey protein concentrate may contain clostridium botulinum, a bacteria that can cause botulism, which affects the nervous and respiratory systems.
The Fonterra bolutism scare affected eight customers whose products, including big brand infant formula and sports drinks, were exported to seven countries including China.
Fonterra let the country down over a botulism scare, its foreign minister Murray McCully said yesterday on a visit to China to try to repair the damage.
McCully told reporters he did not apologize to his Chinese counterpart Wang Yi and State Councillor Yang Jiechi during talks in Beijing, but expressed "regret" toward parents who had been affected by the crisis, AFP reported.
While no infants fell sick as a result of the contamination, the company was accused of mishandling the situation by releasing information too slowly and then giving out incomplete data.
Prime Minister John Key has said he will visit Beijing later this year to personally apologize to Chinese customers.
