The number of Chinese infants sick in hospital after drinking tainted milk formula has doubled to nearly 13,000.
The country's top quality regulator, Li Changjiang, has resigned, according to a report by the official Xinhua news agency, which gave no further details.
Four deaths have been blamed on the toxic milk powder, which causes kidney stones and agonising complications.
Several Asian countries have either banned or recalled Chinese milk products.
The Health Ministry said the number of children hospitalised due to the milk powder contaminated with the industrial chemical melamine rose from a previously announced total of 6,244 - which included many who had left hospital - to 12,892, including 104 who were in a serious condition.
More than 1,500 had already left hospital and nearly 40,000 with milder symptoms received ‘clinical treatment and advice’ before going home.
The scandal that has shaken trust in Chinese products after last year's scares over toxic and shoddy goods from toothpaste and drugs to pet food and toys.
Melamine has also been found in cartons of milk and some dairy exports, but no illnesses from those sources have been reported.
Chinese Premier Wen Jiabao visited hospitals in the national capital in a bid to reassure an anxious public. But he also said the outbreak of poisonings exposed deeper failings.
He also vowed stiff penalties if the problem re-emerges.
China's food quality watchdog has said it found melamine in nearly 10% of milk and drinking yoghurt samples from three major dairy companies.
At the weekend, a three-year-old Hong Kong girl was found to have a kidney stone after drinking a milk product tainted by melamine, making her the territory's first suspected victim.
Hong Kong's government today approved a law strictly limiting melamine in food.
The regulation on melamine concentration, which takes effect tomorrow, is stricter than those imposed by the EU and the US.
Nestle, the world's largest food company, said today it has recalled a UHT pure milk product in Hong Kong after Centre for Food Safety discovered samples containing a tiny amount of the chemical.
