Inspectors from south China's Guangdong Province have found banned substances in frozen pig kidneys imported from the United States and frozen pork spareribs from Canada, the quality control watchdog has announced.

The 16.67 tons of frozen pork kidneys and 21.77 tons of frozen pork, imported through the province's Panyu port, were returned to exporters, the General Administration of Quality Supervision, Inspection and Quarantine said in a statement published on its website.

Without identifying the export companies, the statement said Guangdong quarantine authorities had found residues of a banned hormone in 10 batches of pork products from the US and one from Canada at the end of last month and "took relevant legal action".

The substance, ractopamine, which promotes the growth of lean meat in pigs and cattle, is banned in China and most other countries, but not in the US and Canada.

The European Union banned its use for edible animals in 1996, and China did so for feedstuff and potable water for animals in 2002.

China's actions followed its earlier suspension of the sale of poultry products from seven US companies after the meat was found contaminated with salmonella, additives and veterinary drugs.

China is a major market for US soybeans and chicken, and sales of citrus, beef and processed food also are growing.

(China Daily, Xinhua News Agency September 19, 2007)