They included 4,246.7 tonnes of milk powder and 1,562.1 tonnes of liquid milk products contaminated with melamine, SAIC statistics showed.

Up to Tuesday, 2.18 million inspectors from industry and commerce departments across China visited 6 million dairy firms. The country has received 310,000 complaints of tainted milk products and replaced 614.5 tonnes of milk for customers.

So far, almost 13,000 infants nationwide have been hospitalized with kidney problems as a result of drinking milk contaminated with melamine. The chemical, which was added illegally, makes the protein content of milk appear higher than it actually.

Sanlu Group, one of the four former famous dairy producers in China, began receiving complaints about sick infants as far back as December 2007, but did not make it known to the public till this month.

The other three milk powder manufacturers, namely Mengniu, Yiliand Guangming, were also exposed as involved in the scandal.

Two high ranking officials, including China's top quality control official Li Changjiang and Wu Xianguo, the Communist Party chief of Shijiazhuang City where the headquarter of Sanlu was based, stepped down on Monday for their poor performance in handling milk contamination cases.