Six Chinese central agents had jointly issued an urgent notice demanding thorough checks on all milk powder and liquid milk products made before September 14, Xinhua has learnt yesterday.

The notice was jointly published by the General Administration of Quality Supervision, Inspection and Quarantine, the Ministry of Industry and Information Technology, the Ministry of Commerce, the Ministry of Health, and among others.

It was the latest aggressive efforts made by the government following the tainted baby formula scandal that killed at least three infants and sickened more than 50,000 others.

All dairy products, which were made before Sept. 14 when China's former major dairy producer Sanlu Group admitted some of its baby milk formula were contaminated with melamine, should be sent for "batch to batch" melamine tests at institutions designated by provincial-level governments, said the notice.

Those which were being sold at supermarkets and shops should betaken off the shelf immediately and their producers should send them to check batch by batch.

The notice also demanded all products that passed the checks should wear a special label on their package before going on sale. While those found to contain excess quantities of melamine should be recalled and sealed immediately.

Dairy products made after Sept. 14 and already tested for melamine tests were allowed to be sold without special labels, it said.

Melamine, often used in the manufacturing of plastics, was added to sub-standard or diluted milk to make the protein levels appear higher.

After the tainted baby formula scandal, the Chinese government had made five rounds of batch checks on dairy products since Sept.14. So far, 531 batches of baby formula from 58 brands and 831 batches of other milk powder from 148 brands produced after Sept. 14 have been tested and none contained melamine.

Last week, the government set temporary limits on melamine content in dairy products. The limits were a maximum of 1 mg of melamine per kg of infant formula and a maximum 2.5 mg per kg for liquid milk, milk powder and food products containing at least 15 percent milk.