Chinese authorities have arrested 22 people in northern China who were allegedly part of a network that produced and sold milk contaminated with the chemical melamine.

The official Xinhua news agency says that among those detained, 19 were managers of 17 pastures, breeding farms and milk purchasing stations.

Police tell Xinhua that the chemical, which is usually used in making plastics, was being produced in underground plants and then sold to breeding farms and purchasing stations.

Chocolates of British chocolate maker Cadbury are displayed for sale at a supermarket in Hong Kong, 29 Sep 2008

The arrests come as British candy maker Cadbury announced the recall of 11 varieties of Chinese-made products from shelves in China, Taiwan and Australia.

Melamine-laced infant milk has already sickened some 53,000 babies in China. Four children have died after drinking milk or milk products laced with melamine.

A statement today from Cadbury says it issued the recall because of concerns about the possibility of melamine contamination in its chocolates.

Cadbury says it has carried out tests of its chocolates made in China and the results have cast doubt on the integrity of its products.

The chocolates are mostly distributed in Taiwan and Hong Kong, but one product line is sold in Australia.

Since the scandal broke earlier this month, more than 50 governments in Asia, Africa, Europe, Latin America, North America and the Middle East have either banned or recalled Chinese-made products containing milk.

Some information for this report was provided by AFP.