BEIJING - China on Wednesday announced standards for levels of the industrial chemical melamine permitted in milk and food products as it seeks to rein in a festering safety scare.

The government has been struggling to deal with the health and public relations issues stemming from the scandal, which erupted last month and is increasingly affecting China's food exports.

The crisis has been blamed on dairy suppliers who are accused of adding melamine to watered-down milk to fool quality control tests and make the product appear rich in protein.

Melamine, used in products including plastics, paint and adhesives, can lead to kidney stones and possibly life-threatening kidney failure.

The deaths of at least four babies in China have been blamed on the chemical and more than 54,000 children have been sickened.

Wang Xuening, a Health Ministry official, on Wednesday acknowledged that small amounts of melamine can leech from packaging into milk and other foods, but said deliberate tainting is forbidden.

"For those who add melamine into food products, their legal responsibility will be investigated," said Wang, who is the deputy director of the ministry's health supervision bureau.

Safe melamine limits were set at 1 part per million of infant formula and 2.5 parts per million for liquid milk, milk powder and food products that contain more than 15 per cent milk.

There had been no previous standards and levels of melamine discovered in batches of milk powder recently registered as much as 6,196 parts per million. Chinese health officials have said no harm comes from consuming less than 0.63 parts per million.

Brazil on Tuesday became the latest of dozens of countries to restrict Chinese food products. It banned all such imports because of safety concerns.

Brazil's food imports from China are minimal - in 2007 the country bought just $120 million in such products.

The Philippine health secretary said Wednesday that traces of melamine have been found in a third imported Chinese-made milk product, Jolly Cow Slender Milk, which had already been taken off shelves.

China's Cabinet has already acknowledged that the country's dairy industry was "chaotic" and suffered from a grave lack of oversight. It has pledged to monitor milk products from dairies to store shelves.

The State Council has also ordered hospitals to provide free treatment for sick infants.

The crisis has forced the government to fire local and even high-level officials for negligence, while repeating earlier promises to raise product safety standards.