Chinese authorities ordered the recall of tainted leukemia drugs blamed for leg pains and other problems, state media reported, the latest crisis to strike the country's embattled food and drug industries.

Most of the drugs involved — methotrexate and cytarabin hydrochloride — have been recovered and authorities have traced the remainder, the Xinhua News Agency said Sunday. The report did not say if any of the drugs had been exported.

Authorities have banned the sale and distribution of the drugs, produced by the Shanghai Hualian Pharmaceutical Co., it said.

China, a major global supplier, has been facing growing international pressure to improve the quality of its exports after dangerous toxins were found in goods including toys and toothpaste.

Xinhua on Saturday announced that inspectors recently found residue of the banned stimulant ractopamine in frozen pig kidneys imported from the United States and frozen pork spareribs from Canada. The names of the exporting companies were not identified. Ractopamine is forbidden for use as veterinary medicine in China.

Ractopamine, a hormone that promotes the growth of lean meat in pigs and cattle, is banned by China and most other countries as a health hazard, although its use in stock animals is permitted in the U.S. and Canada. China has also recently banned imports of U.S. meat contaminated with salmonella, additives and veterinary drugs.

Xinhua said the 16.67 tonnes of frozen pork kidneys and 21.77 tonnes of frozen pork had been returned to importer exporters, said the General Administration of Quality Supervision, Inspection and Quarantine.

Xinhua said the State Food and Drug Administration and Health Ministry banned the two leukemia drugs after several child leukemia patients who were taking them complained of leg pains and difficulty walking. Xinhua said some patients also complained of urine retention.

It said the Health Ministry and drug administration had traced the problems with the drugs to their being tainted with vincristine sulfate, an anticancer drug. Xinhua said factories manufacturing the drugs had been closed.

China has taken a series of steps to crack down on tainted drugs and other unsafe products, in part because of concern over the reputation of its exports.

In the harshest action so far, the country's former top drug regulator was executed in July for taking millions of dollars in bribes to approve substandard medicines, including an antibiotic that killed at least 10 people.