A day after firing China's top quality regulator over the tainted milk scandal that has killed four infants, Beijing has vowed to prevent tainted milk products from reaching processors or export markets.

Panic over the tainted milk, which made a total of 53000 ill, has spread to many Asian and African countries where not only baby formula but ice bars and yoghurt have been contaminated with the industrial chemical melamine. Melamine can cause kidney stones, organ failure and other agonising complications when consumed in excessive amounts by infants.

The extent of the cover-up by milk producers and authorities, anxious that publicity could further damage the 'Made in China' marque and tarnish the country's reputation during the Beijing Olympics was gradually becoming clear.

Agriculture Minister Sun Zhengcai said he would wage a "battle" to clean up the merchants blamed for selling adulterated milk on to dairy companies. He said: "There can be no compromise in fulfilling every task of the clean-up."

The minister singled out the milk stations that collect fresh supplies from often scattered farms. They have been blamed for watering down milk and adding nitrogen-rich melamine, fooling quality checks measuring protein, which is also rich in nitrogen.

Many of these stations were unregistered and unregulated, Mr Sun said. "The intermediate link in purchasing raw milk is basically out of control. These grave problems and this state of disorder have reached the stage where a clean-up is unavoidable."

After several days of silence on how many toddlers had been affected, China revealed the number had doubled to nearly 13,000 with more than 80 percent of the sick being toddlers under two. Nearly 53,000 had been found with milder symptoms after alarmed parents poured into hospitals nationwide to seek treatment for their ailing only child born under the strict 'one couple, one child' family planning policy.

Underscoring how seriously China's leaders are treating the latest food safety scandal to shake confidence in domestic manufacturers, the government sacked Li Changjiang, head of the General Administration of Quality Supervision, Inspection and Quarantine. State media, which has kept a tight grip on reporting of the scandal, said: "Li was the highest ranking official brought down so far by the dairy product contamination scandal."

The Communist Party boss of the northern city of Shijiazhuang, the base of the Sanlu Group whose milk powder has been blamed for the most serious cases, was also fired.

But Sanlu had been receiving complaints of children sickened after drinking its milk powder since last December, the Xinhua news agency reported, citing a cabinet investigation. Communist officials in the north Chinese city of Shijiazhuang, where Sanlu is based, delayed referring the matter to higher authorities for more than a month after they finally were told of it in early August.

The report, the first official admission of deliberate delays in reporting the dangers, said: "They violated rules on reporting major incidents involving food safety."

Reports of tainted milk only emerged in state-run media earlier this month, after prompting from the New Zealand partner of Sanlu.

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