Market regulators in Xiangfan of Central China's Hubei province have started an "all-out search" for a batch of dairy products that is believed to contain melamine - a toxic industrial chemical that killed at least six infants and sickened about 300,000 children across the country in 2008.

The administration for industry and commerce in Xiangfan issued an urgent notice on Nov 15 asking all local businesses to look for 50 packages of a type of corn-flavor dairy beverage. It is unclear how many bags or boxes a package contains.

The notice said the beverage might have entered the local market, but as of early last week, local authorities could not find any trace of them.

Tests showed that the melamine level in the beverage measured as high as 4.8 milligram (mg) per kg, according to the notice.

A reading above 2.5 mg per kg for such a beverage suggests that melamine was added as an ingredient during production deliberately, according to a standard introduced in October 2008, a month after the melamine scandal broke out.

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Chen Min, deputy head of the publicity department in Xiangtan city of Hubei's neighboring Hunan province, told China Daily on Sunday that the beverage sought in Xiangfan was actually produced by a manufacturer based in Xiangtan.

"For producing the beverage, the company had bought 25 kg of milk powder as raw material from a supplier from another province without knowing the milk powder was tainted with melamine," Chen said over the telephone, referring to a company called Xiangtan Yuanshan Dairy Industry Company.

He said the raw material supplier had offered all quality reports required, so the company did not conduct a check.

Chen said as many as 300 packages of the beverage had been produced. The company had halted the beverage's production since June 15 and the products were mainly shipped to mid- and small-sized cities close to Xiangtan city.

The latest revelation in Xiangfan added to a spate of aftermath discoveries of melamine-tainted dairy products earlier this year.

In March, several Shanghai company executives were held responsible for the chemical's misuse and sentenced to jail terms.

Sang Liwei, a food safety lawyer in Beijing and representative of a nonprofit organization, the Global Food Safety Forum, said loopholes in the administrative supervision and manipulative manufacturers trying to get away with unqualified products are the major causes of melamine-tainted products reemerging.

"The country's food safety watchdog ordered that all tainted milk powder be destroyed after the 2008 melamine scandal. But the government did little to ensure the order is implemented," Sang said, adding upper level administrations placed the orders without setting up a compulsive tracing system.

"The key lies in effectively punishing manufacturers and officials involved," he said, adding an independent team of food safety officers should be set up in all food manufacturing companies.

Song Quanhou, director of the National Food Quality Supervision and Inspection Center, seconded Sang.

"Setting up a position for an independent food safety officer in a company, who reports directly to local food safety watchdogs and industry associations, will bring efficiency to the current supervision system," Song said.