After a nationwide inspection, the chemical that has killed three babies and sickened more than 6,000 others was found in the products of 22 Chinese companies.

China’s quality watchdog, the State Administration of Quality Supervision, Inspection and Quarantine (AQSIQ) announced late September 16 that 69 batches of baby formula made by 22 producers were found to be contaminated by melamine, a chemical that can cause kidney troubles in infants. Their investigation covered a total of 491 batches from 109 companies across China. The government has ordered an immediate halt on the sale of all tainted formula.

Some of China’s most famous brands were implicated in the scandal. Formula from Shengyuan, Guangming, Yashili, as well as Beijing Olympics sponsor Yili and Hong Kong-listed Mengniu were all found to contain melamine.

Two of the 22 companies have exported contaminated products abroad. Guangdong's Yashili Group and Qingdao's Suncare sent their baby formula to Yemen, Bangladesh, Myanmar, Gabon and Burundi. Both companies have started a mass recall.

When news of the contaminated baby formula broke last week, Sanlu Group of Hebei Province was fingered as main source of tainted product. It now appears that the problem was far more endemic.

A sample of formula produced by Sanlu Group’s plant in Shijiazhuan, the capital city of Hebei, had concentrations of melamine as high as 2,563 milligrams per kilo. According to the U.S. Food and Drug Administration, a one-year old baby can endure 6.3 milligrams of melamine per day. The most contaminated samples of Sanlu’s baby formula contained 40 times that.

Sanlu made a public apology on September 15 and has fired its chairwoman and general manager, Tian Wenhua. Four city officials in Shijiazhuan, where Sanlu is based, have also been removed from their posts.

As of September 16, police have arrested four suspects who confessed to adding melamine to milk. Another 22 have been detained.

Hebei and Inner Mongolia were found to have the most contaminated products among China’s major milk producing regions.