Officials have ordered "batch to batch" tests, Xinhua reported, citing sources. Supermarkets have been told to send products on the shelves for testing.

The testing labs are to be designated by provincial governments. Batches that pass the test can be returned to store shelves with special labels saying they have been tested.

On Sept. 14, Sanlu Group admitted that it had produced baby formula contaminated with melamine, a chemical used to harden plastics. Thousands of babies have been sickened and at least three died.

Melamine is sometimes added to watered-down milk to increase its apparent protein content.

The government has tested 531 batches of formula and 831 of other powdered milk products, with all found to be free of melamine. The baby formula was marketed under 58 brand names and the other products under 148.