China's health minister said tainted milk formula had killed three babies and made 6,200 ill.
The deaths prompted three additional companies - including the country's biggest dairy - to recall products.
Officials said that about 20% of the dairy companies tested had sold products tainted with melamine. Suppliers to the companies are thought to have added the banned chemical, normally used in plastics, to raw milk to make the milk appear higher in protein.
The companies included Mengniu Dairy, China's biggest milk company, which said it was recalling its baby formula after government tests found melamine in the product. The announcement said the recall covers three batches of formula made in January but gave no details on how much product will be affected. It did not say whether any of Mengniu's baby formula was exported.
Health minister Chen Zhu told a televised news conference that 6,244 babies had been ill after being feed tainted milk formula and that 158 were suffering from acute kidney failure.
The head of China's quality watchdog, Li Changjiang, said that in addition to the company at the heart of the food scandal, Sanlu Group and Mengniu, two other companies, Guangdong-based Yashili and Qingdao-based Suncare, were recalling their products.
The General Administration of Quality Supervision, Inspection and Quarantine had already reported that its inspectors had found melamine "in 69 batches of milk powder manufactured by 22 companies".
The nationwide inspection by China's quality watchdog agency took test samples from 109 companies that produce baby milk powder in China. Mr Li said another 66 companies had stopped production before the melamine problem emerged.
Yashili exported its products to Bangladesh, Yemen and Myanmar, but AQSIQ said initial testing of samples of the company's exports turned up no trace of melamine.
In Hong Kong, food inspectors ordered a recall after melamine was found in an ice cream bar made by Shanghai Yili AB Foods. The amounts of the chemical found "would not pose major health effects from normal consumption of the bar, however, small children should not eat it," the Centre for Food Safety said on its website.