The price of raw heparin, which is extracted from pigs, doubled four months before users of the drug in the United States suffered severe and sometimes fatal allergic reactions.

The Chinese drug information company, Healthoo.com, suggests a link between raw materials -- not processing -- and the price increase, The Washington Post reported Sunday.

Health officials found in March that 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.

Some in the pharmaceutical industry charge the company that purchases the raw material from China, Scientific Protein Laboratories of Wisconsin, with pocketing extra profits as a result of using the cheaper version of chondroitin.

U.S. Food and Drug Administration officials could not determine if the contamination was deliberate, though tests concluded the chondroitin was manufactured to escape quality-control tests.