China's drug watchdog said on Wednesday it is continuing its probe into methotrexate, a drug routinely prescribed to treat acute leukemia and rheumatoid arthritis, but had eliminated production errors as a cause of the problems.

The drug, made by Shanghai Hualian Pharmaceutical Co., was suspended from sale and use after adverse reactions were reported on July 6 in several juvenile leukemia patients in three hospitals in Guangxi Zhuang Autonomous Region and Shanghai, according to the State Food and Drug Administration (SFDA).

SFDA Deputy Director Wu Zhen said "the team sent to reevaluate the drug has uncovered no problems with the raw materials used to make the drug or any violations of production procedures."

He added that investigators were shifting their attention to transportation, storage, and administration of the drug.

Wu said possible adverse reactions to methotrexate are clearly stated in the drug information.

"However, it is abnormal for so many patients to have adverse reactions in the same short period of time after being injected with batches 070403A and 070403B of the drug," he said.

"We'll keep the public informed about the state of our investigations," he promised.

Some children felt pain in their legs and some experienced difficulty walking after being injected with the drug.

According to WHO statistics, there have been 12,502 reports of adverse reactions to methotrexate worldwide, including a handful of very serious cases.

(Xinhua News Agency July 12, 2007)