China has arrested two brothers suspected of adding an industrial chemical to milk they sold to a company that produced infant formula. The tainted milk powder has killed two babies and sickened more than 1,200 others. Stephanie Ho reports from Beijing.

Hebei Province police spokesman Shi Guizhong announced the first two arrests on state television Monday. Shi says two brothers, surnamed Geng, were taken into custody on suspicion of producing toxic and hazardous foodstuffs.

The Geng brothers ran a milk collection center in Hebei Province that provided milk to the Hebei-based Sanlu Group to make into infant milk powder.

Official media reports say the Geng brothers had been selling three tons of contaminated milk per day to Sanlu since the end of last year. They are alleged to have put the banned industrial chemical melamine into the milk to make it appear to have a higher protein content.

Melamine was linked to deaths and illness of thousands of cats and dogs in the United States last year after it was added to pet food ingredients exported from China.

The world's biggest milk trader, New Zealand-based Fonterra, owns a 43-percent stake in Sanlu, which is China's largest milk powder producer.

New Zealand Prime Minister Helen Clark Monday said she had ordered her senior officials to directly inform senior officials in Beijing after it appeared the local officials were dragging their feet in ordering the recall.

Baby suffering from a kidney stone after drinking Sanlu brand milk powder rests at a hospital in Ziyang of southwest China's Sichuan province,13 Sept. 2008

Fonterra has said it urged Sanlu to recall the tainted product as early as six weeks ago, which was right before the start of the Olympics. Sanlu ordered the recall last Thursday.

Chinese officials have defended their response to the latest product safety disaster and blamed Sanlu Group for delays in warning the public.

Chinese officials have spread out across the country to inspect dairy companies and remove all substandard milk powder from the market. The contaminated infant formula has killed two babies and has caused more than 1,200 other infants to develop kidney stones.