Sanlu made the information about the contamination of its products public last week after its New Zealand stakeholder, Fonterra - a global supplier of dairy ingredients - informed the New Zealand government, which then told the Chinese government.
Li Changjiang, head of China's quality control watchdog, said that two companies - Yashili and Suncare - exported milk powder and they were recalling their products.
He said that melamine had also been found in a yogurt ice-bar made by Yili, one of China's biggest dairy producers, and sold in Hong Kong.
The brand has now been recalled by the Hong Kong supermarket chain Wellcome.
Mr Li, head of the state quality supervision body AQSIQ, said China would adjust its baby formula standards to allow tests for poisonous substances such as melamine.
He said tests for the substance had not been made before, because it was banned from food products.
The BBC's James Reynolds in Beijing says China is keen to try to reassure parents that it is in control of what is happening.
This scandal has undermined confidence in food safety in China and many parents are worried about what they will feed their babies, he adds.
Analysts say the incident is an embarrassing failure for China's product safety system, which was revamped after a spate of international recalls and warnings last year over a range of goods.
Meanwhile, rising public anger, expressed on China's active internet forums, is prompting reports of a crackdown by the government on reporting of the scandal.
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