More than 50,000 children in China have been reported ill
Countries across Asia are testing Chinese dairy products as fears spread over melamine-tainted milk - and some have banned these products outright.
Four Chinese children died after drinking contaminated milk and 13,000 others remain in hospital.
Four children in Hong Kong have now been diagnosed with kidney stones after drinking milk from the mainland.
The company at the centre of the scare, Sanlu, failed to report the health problems for months, state media say.
Sanlu began receiving complaints about sick children as early as last December but did not report the issue to the authorities until early September, according to a CCTV report citing an official investigation.
The report appears to be the first official admission that news of the health scare was deliberately suppressed.
Brunei, Indonesia, Singapore, Malaysia, Hong Kong, Taiwan, Japan, Bangladesh, Gabon, Burundi and the Philippines are all either testing Chinese diary products or pulling them from shops.
Many countries have recalled products which could be affected
US coffee giant Starbucks has stopped serving drinks with milk in many Chinese outlets and many other large companies are testing products in some Asian locations or pulling them straight from the shelves.
Malaysia has expanded its ban on dairy products to include candies, chocolates and all other foods containing milk, an official there has confirmed.
In Japan, one major supplier has pulled buns made from Chinese milk from supermarket shelves and a petition signed by regional governors urges the central government to suspend imports of all Chinese dairy products.
The problem was first revealed two weeks ago, when milk powder from the Sanlu Group was found to contain melamine, an industrial chemical.
At least 22 other companies have since become involved in the scandal and milk products made by the Yili, Mengniu and other groups have been recalled from supermarket shelves in China and many other countries.
Many parents across Asia are concerned that their children may have drunk the affected milk.
"I'm still worried about my child," said Mary Yu, a Hong Kong mother who took her 3-year-old son for hospital tests on Tuesday, along with dozens of other parents.
"I want to have a thorough check to play it safe," she told the Associated Press.
Melamine is used in making plastics and is high in nitrogen, which makes products appear to have a higher protein content.
Health experts say that ingesting small amounts does no harm but sustained use can cause kidney stones and renal failure, especially among the young.
One result of the scare is that wet nurses around China are now in huge demand, according to the Chinese media.