BEIJING (AP) -- Melamine-tainted dairy products were pulled from convenience store shelves in southern China more than a year after hundreds of thousands of children had been sickened in a massive milk safety scandal, a government spokeswoman said Monday.
The announcement calls into question the effectiveness of a crackdown launched by Chinese officials to improve product safety after a number of scandals, including the contamination of baby formula in 2008 and the recent discovery of the toxic metal cadmium in cheap jewelry.
Frozen milk products and cartons of milk dating from early 2009 were taken off the shelves after health inspectors tested them and found melamine, said Ling Hu, a Guizhou provincial government spokeswoman.
She said the provincial health bureau was checking to see why the products were not pulled from the shelves earlier. Calls to the Guizhou health bureau ran unanswered Monday.
Tainted products from three companies -- Shandong Zibo Lusaier Dairy, Liaoning Tieling Wuzhou Food, and Laoting Kaida Refrigeration -- were discovered in more than a dozen convenience stores around the province, Ling said.
Laoting Kaida Refrigeration was among companies named in the original melamine scandal in 2008, when six children died and 300,000 were sickened after drinking baby formula with melamine, used in the manufacture of plastics and fertilizer.
The official China Daily newspaper quoted Wang Dingmian, former chairman of the Guangdong Provincial Dairy Association, as saying tainted milk products recalled at the time somehow made their way back onto the market. He said the latest discoveries of contaminated dairy exposed weak government regulation.
Melamine, which can cause kidney stones and kidney failure, was added to watered-down milk to fool inspectors testing for protein and stretch profits. Both melamine and protein are high in nitrogen. Dozens of officials, dairy executives and farmers were punished.
Since the scandal broke, China vowed to implement stricter safety measures and step up inspections on the dairy industry. Ling said health officials have continued to target distributors who sell melamine-tainted milk to stores, but some distributors, wrongly assuming the government scaled back its crackdown, continue to sell it.
Ling said distributors arrested for selling tainted milk likely led authorities to the convenience stores where the contaminated product was found. She had no other details and said the investigation was still under way.
Earlier this month, government officials said the Shanghai Panda Dairy Co. had been under a secret investigation for nearly a year before announcing it produced melamine-tainted milk.
China's troubles in cleaning up its food supply chain reflect problems it has had coupling its rapid growth with product safety in other areas.
Earlier this month, an investigation by The Associated Press found 12 of 103 pieces of Chinese-made children's jewelry bought in U.S. stores contained at least 10 percent cadmium, some in the 80 percent to 90 percent range.
Cadmium, like lead, can hinder brain development in young children, according to recent research, and also causes cancer. China has not commented on reports of the cadmium problem.
The U.S. Consumer Product Safety Commission warned parents to "safely dispose" of any cheaply made jewelry or trinkets, most of which are imported from China.