HONG KONG, China (CNN) -- The fallout from a tainted milk scandal in China continues to spread around the globe, with tainted crackers found in South Korea, two more illnesses reported in Hong Kong and a grocery chain in Great Britain pulling Chinese products.
The United States, meanwhile, said inspectors would expand testing for Chinese products that may contain high levels of milk or milk proteins.
Nearly 53,000 children in China have been sickened by infant formula or other products contaminated with the chemical melamine. Four babies have died. About a dozen countries, from Asia to Africa, have banned or recalled Chinese milk products.
In South Korea, the government banned the importation of all Chinese products containing milk after Chinese biscuits tainted with melamine were discovered in the country, a government spokesman said Wednesday.
A formal announcement was expected on Thursday, but the ban went into effect Wednesday night, the spokesman for the Korean Food and Drug Safety Authority said. Watch the fallout from the scandal »
The biscuits, called Me Sarang Custard, are sold under the label of a popular South Korean confectioner called Haitai, but are produced in China.
In Hong Kong, health officials reported two new cases of kidney stones in children who have consumed melamine-tainted dairy products. A pair of boys from mainland China -- ages 2 and 9 -- were diagnosed with the condition at local hospitals, the government's Centre for Health Protection said Tuesday.
The latest cases of kidney stones bring to four the confirmed number of illnesses in Hong Kong caused by the consumption of contaminated milk products.
Authorities in China have arrested 18 people in a nationwide investigation. They include two brothers who face charges of selling contaminated milk; the brothers could face death if convicted, according to China Daily, a state-run newspaper. Watch the government's reaction to the scandal »
The raw milk used to produce powdered baby formula had been watered down, and the chemical melamine was added to fool quality checks, the newspaper said.
Hong Kong's Centre for Food Safety said it has found trace amounts of melamine in White Rabbit Creamy Candy and Four Seas Cake (strawberry flavor). Authorities have asked retailers to stop selling the products, and importers will recall them, the government said.
In the United Kingdom, the supermarket chain Tesco said Wednesday that it had pulled the children's sweets from store shelves over fears they contain melamine. Watch how the scandal has spread beyond milk »
"As a precautionary measure, we have withdrawn White Rabbit Candies from the very small number of UK stores that sell them as part of our ethnic range," a Tesco representative said Wednesday.
In the United States, the Food and Drug Administration said its investigators have not found the Chinese infant formula in question during visits to more than 1,000 stores. Those are mainly in cities with large Chinese communities, such as Los Angeles and San Francisco, California; Seattle, Washington; and New York.
The FDA plans to continue such checks, it said, and "has broadened its domestic and import sampling and testing of milk-derived ingredients and finished food products containing milk, such as candies, desserts, and beverages that could contain these ingredients from Chinese sources."
Meanwhile, health officials in Singapore and Indonesia announced additional recalls of products made with the contaminated milk. Products pulled from store shelves range from flavored milks and ice creams to cookies and candies.
Authorities in a variety of places have stopped importing some Chinese products made from milk, including Indonesia, Taiwan, Japan, Singapore, Malaysia, Burundi, Gabon, Tanzania, Brunei and the Philippines.
Melamine is commonly used in coatings and laminates, wood adhesives, fabric coatings, ceiling tiles and flame retardants. Some Chinese dairy plants have added it to milk products to make it seem to have a higher protein level.
Melamine is the same industrial contaminant from China that poisoned and killed thousands of U.S. dogs and cats last year.
Health experts say that ingesting melamine can lead to kidney stones, urinary tract ulcers, and eye and skin irritation. It also robs infants of much-needed nutrition.
CNN's Andy Saputra, Sohn Jie-Ae and Roya Shadravan contributed to this story.