A Chinese dairy producer at the center of a baby formula scandal has yet to recall 35 tonnes of tainted milk powder from retail outlets and consumers, an official said on Thursday, as it emerged that a fourth child had died.

Local authorities and the Shijiazhuang-based Sanlu Group had recalled 8,875 tonnes of a total of 8,910 tonnes of "problematic" milk powder the company had sold after the scandal was exposed, the city's vice mayor, Zhang Meizhi, told a press conference.

"The departments of quality supervision and industry and commerce in the city are now stepping up efforts to recall the remaining 35 tonnes, especially those sold to consumers in remote areas," she said.

"The milk powder produced before Aug. 6 [tainted products] had all been pulled off shelves," she said.

The company had also sealed off 2,176 tonnes of tainted milk powder it has yet to sell, she added.

The death toll in the scandal has risen to four, the latest being a baby in northwestern Xinjiang Uygur Autonomous Region.

The infant died at a hospital in the Bayingolin Autonomous Prefecture of Mongolian Nationality, the regional health department said on its website (www.xjwst.gov.cn) on Thursday, without giving further details.

The contamination earlier claimed the lives of three other babies, two in northwestern Gansu Province and one in eastern Zhejiang Province.

Nationwide, more than 6,200 infants have developed kidney stones after drinking Sanlu's baby formula, tainted with the chemical melamine, which was believed to have helped to increase protein content.

The dairy giant Sanlu, based in the Hebei provincial capital of Shijiazhuang in north China, was the first company exposed in the scandal. It is 43 percent-owned by New Zealand dairy company Fonterra and has been ordered to halt all production.

Tian Wenhua, the sacked board chairwoman and general manager of Sanlu, has been detained by police for questioning.

The State Administration of Quality Supervision, Inspection and Quarantine has carried out test samples involving 491 batches of products sold by all 109 companies that produced baby milk powder in the country. The inspectors found melamine in 69 batches of powder from 22 companies.

To date, 18 suspects in Shijiazhuang have been arrested. Six were charged with selling melamine, while the other 12 were dealers suspected of selling contaminated milk to Sanlu, Shi Guizhong, spokesman for the Hebei Provincial Public Security Department, told reporters on Thursday.

On Wednesday the mayor of Shijiazhuang Ji Chuntang resigned as a result of the scandal.

Earlier on Tuesday, four city officials were fired. They included Zhang Fawang, vice mayor in charge of agricultural production; Sun Renhu, the Animal Husbandry and Fishery Bureau director of Shijiazhuang; Zhang Yi, Food and Drug Administration director; and Li Zhiguo, director of the Bureau of Quality and Technical Supervision.

(Xinhua News Agency September 19, 2008)