Jin Shaohong, deputy director of China's National Institute for the Control of Pharmaceutical and Biological Products, said study on heparin-related adverse effects indicated "the direct causal relationship between the heparin substitute (hypersulphated chondroitin sulphate) and the clinical cases of deaths cannot yet be confirmed," reported Xinhua, China (OTCBB:XHUA)'s official news agency.

U.S. health officials found in March heparin made in China and distributed by Baxter International (NYSE:BAX) was contaminated with an altered version of chondroitin, a substance found in cartilage and used to treat some forms of arthritis, prompting Baxter to initiate a massive recall.

Other countries using heparin products containing a "heparin-like substance" hadn't reported adverse reactions, Jin said.

"U.S. experts also analyzed that the concentrated heparin adverse events which occurred in the U.S. had a certain relationship with the large dose of clinical use and quick injecting speed," he said.

Jin said Baxter didn't carry out "necessary" cooperation with Chinese experts sent to the United States to investigate the cause of the contamination, Xinhua said.