Four infants have died and more than 6,000 are sick
The scandal of tainted dairy products in China has widened, with liquid milk now found to be contaminated.
Inspectors found that 10% of liquid milk taken from three dairies was tainted with melamine.
The scandal first came to light in milk powder that killed four infants and sickened more than 6,000 others.
Melamine, an industrial chemical normally used in plastics, is believed to have been added to diluted milk to make it appear higher in protein.
China's quality watchdog, the General Administration of Quality Supervision, Inspection and Quarantine, tested liquid milk from three dairies.
Its website said 10% of the milk from the country's two largest - Mengniu Dairy Group and Yili Industrial Group - contained up to 8.4 milligrams of melamine per kg.
Products from Shanghai-based Bright Dairy were also contaminated, it said.
The watchdog said it would "strictly find out the reason for adding the melamine and severely punish those who are responsible".
All the batches that tested positive were being recalled, it said.
Soon after the announcement, Hong Kong's Wellcome and Park'n Shop supermarkets said they were pulling Mengniu products off their shelves.
Yili group products were recalled by the Hong Kong government on Thursday, after tests found milk, ice-cream and yoghurt to be contaminated with melamine.
Chinese officials have insisted that most milk is safe to drink - in an attempt to rebuild public trust in dairy products.
The BBC's James Reynolds in Beijing says it is not being suggested that anyone has fallen ill from drinking liquid milk contaminated with melamine.
The scandal broke at the Sanlu Group
But he says people are extremely angry to learn that more and more products have been found to be unsafe.
One 31-year-old man queuing at Sanlu offices in Shijiazhuang to get a reimbursement for medical exam payments for his baby told Associated Press news agency: "If such a big company is having problems, then I really don't know who to trust."
The scandal broke last week after the Sanlu Group said it had sold melamine-laced milk powder.
Chinese police have arrested 18 people in connection with the scandal.
Of those children made sick, more than 150 are said to have acute kidney failure.
China's ability to police its food production industries has long been under question.
Health scares and fatalities in recent years have ranged from the contamination of seafood to toothpaste and, last year, to pet food exported to the US.