"Considering the particular characteristics of food products and the complexity in the cause of food safety problems, and with a view to further enhancing supervision over food producers, ensuring food safety and protecting consumers' interests," said the State Administration of Quality Supervision, Inspection and Quarantine (AQSIQ) in an explanation of the move.

It said relevant companies must stop activities of publicizing their national inspection exemption qualifications. The national inspection exemption labels printed on food products and their packages became invalid from Wednesday.

To help companies avoid repeated examinations and reduce their burden, the country began exempting those producing top-quality and globally-competitive products from quality inspections in 2000. According to previous regulations, any company in China could apply for the inspection-exemption if they had a long standing quality record, large market share, and implemented standards up to or above national or international levels.

The products that passed state or province-level inspections on three consecutive occasions were awarded the qualification. While producers still must report the inspection-free products' quality status on a regular basis, AQSIQ organized spot checks on these products annually.

Before the move, AQSIQ had cancelled the exemption qualification of Shijiazhuang-based Sanlu Group and the "Famous Brand" titles of its baby milk powder, other kinds of milk powder and sterilized milk.

It was amending quality standards of dairy products targeting non-food additives. It would adjust its baby formula standards to allow tests of poisonous substances such as melamine.

No melamine tests were conducted on dairy products in the past. New standards would be published later this year, AQSIQ said.

The country's Certification and Accreditation Administration also said on Wednesday it revoked all certificates given to Sanlu and its products, including the sanitation registration qualification of food for export.

The government on Wednesday announced comprehensive nationwide tests for melamine on every dairy product by every producer after a third infant died after drinking contaminated milk powder.

The latest fatality occurred in the southeastern Zhejiang Province, Minister of Health Chen Zhu told a press conference in Beijing. He gave no further information about the latest fatality.

The first two deaths both occurred in northwest Gansu Province. A five-month-old boy died on May 1 and an eight-month-old girl succumbed on July 22.

Both were fed with Sanlu formula and had suffered kidney failure

Another 6,244 infants were ill after consuming the tainted formula as of 8 a.m. on Wednesday, including 158 with acute kidney failure, of which 94 were in stable condition, Chen said.

Inspectors had found the chemical in 69 batches of baby milk powder produced by 22 companies nationwide. The seized items included such well-known brands as Sanlu, Mengniu, Yili and Yashili, among others.

The State Administration for Industry and Commerce, which supervises product quality at the retail level, on Wednesday ordered all the tainted products to be immediately removed from shelves.

The contaminated products were to be sealed at the site and kept from re-entering the market.

New Zealand dairy giant Fonterra, which owns a 43-percent stake in Sanlu, said on Tuesday its own Chinese business had voluntarily recalled one batch of Anmum Materna milk.

The company said the particular batch had been manufactured and distributed under licence by Sanlu using what it believed to be contaminated local raw milk.

Melamine is a toxic chemical, banned in food. It is rich in nitrogen and was illegally added to raw milk for protein tests that raise nitrogen levels.