BEIJING — China said Sunday the number of children sickened by baby formula tainted with the banned industrial chemical melamine has doubled to nearly 12,900 as the government confronts a scandal over widespread contamination of the milk supply.

More than 80 percent of the 12,892 children hospitalized in recent weeks were 2 years old or younger, the Health Ministry said. Four children have died.

The ministry said most of the children sickened consumed infant formula from one company, the Shijiazhuang Sanlu Group Co. The dairy is at the center of one of China's worst food safety scandals.

In the two weeks since the government first acknowledged the contamination, it has issued recalls for dairy products from 22 companies after tests turned up traces of melamine. The Health Ministry said that most of the hospitalized were sickened by powdered milk and formula.

Melamine is used in making plastics and is high in nitrogen, which registers as protein in tests of milk. Though health experts believe ingesting minute amounts poses no danger, melamine can cause kidney stones, which can lead to kidney failure. Infants are particularly vulnerable.