Beijing ? China’s State Council tightened quality control regulations for the dairy industry Friday, as authorities in Macau and Hong Kong reported several children had kidney stones blamed on Chinese tainted milk.

Contaminated milk powder, laced with the industrial chemical melamine, has been blamed for causing the deaths of four infants and sickening more than 54,000 others.

More than 10,000 children remained hospitalized with eight of them in serious condition, the Health Ministry said.

The new regulations, effective immediately, tighten control over cattle breeding, the purchase of raw milk and the production and sale of dairy products, the official Xinhua News Agency said.

The measures also increase punishments for those caught violating safety standards.

On Friday, police in northern Hebei province arrested a suspect accused of producing 600 tons of melamine-spiked protein powder, Xinhua said. Eight dairy farm owners and milk buyers were also arrested purchasing the powder, it said.

In Hong Kong, a 10-year-old boy was diagnosed with two kidney stones, the Department of Health said, raising the total number of children with milk-related kidney stones to seven in Hong Kong and Macau.

Meanwhile, Macau’s Health Bureau said three girls between the ages of 4 and 7 have developed kidney stones. Their conditions were not immediately known.

The boy has been drinking high-calcium, low-fat milk made by the Chinese dairy Yili Industrial Group Co. everyday for the past six years, the health department said. He is in stable condition and does not require hospitalization.

Also Friday, parents of an 11-month-old diagnosed with kidney stones filed a lawsuit against the Sanlu Group Co. – the dairy company at the heart of the tainted milk crisis.

It is the second known lawsuit against the company, whose baby formula was to contain high levels of melamine.

Earlier this month, parents from central Henan province filed suit against Sanlu, seeking $22,000 in compensation for medical, travel and other expenses incurred after their 14-month-old baby developed kidney stones.

It is not clear if courts will allow these suits to progress as product liability lawsuits are still relatively rare in China, and lawyers have complained of government pressure to withdraw from the cases.

Chinese authorities believe dairy farmers added melamine – used in plastics, paint and adhesives – to watered-down milk to make the product appear rich in protein and fool quality control tests.

The practice was apparently widespread in the industry, with government investigations finding 37 Chinese dairy companies, including the most reputable brands, had sold tainted products.

Police have arrested 36 people in connection with the scandal in Hebei, where Sanlu is headquartered, Xinhua said.

The scandal has sparked global concern about Chinese food imports, with more than 30 countries restricting Chinese dairy products, and in some cases all Chinese food imports.