Federal regulators have been able to tie tainted heparin sold by Baxter international to three deaths, out of 93 investigated by the Food & Drug Administration (FDA).

According to an article in The Chicago Tribune, the FDA said it completed its review of the death reports related to heparin that the agency received from Jan. 1 to March 31, when reports of heparin adverse reactions peaked. Of 10 reports of death from severe anaphylaxis or hypotension, three of those could be traced to lot numbers of Baxter products that tested positive for chondroitin sulfate. Heparin lot numbers were not known for the other seven deaths, so the FDA could not determine if those patients received tainted heparin.

Of the remaining 83 reports, the FDA described 13 as “potential complications of heparin use” such as bleeding; 25 cases were due to causes unrelated to heparin use such as pneumonia, sepsis and kidney failure. The FDA said that there was insufficient information available about the remaining 45 fatalities to conclusively cite a cause of death.

In January, Baxter International recalled nearly all its heparin injections in the US after some patients experienced extreme – and in some cases fatal – allergic reactions, including difficulty breathing, nausea, vomiting, excessive sweating, and rapidly falling blood pressure that was life threatening after being administered the products. There have been similar recalls by other manufacturers of Chinese-sourced heparin in Denmark, Italy, France Germany and Japan. In total, the FDA said tainted heparin has been identified in 12 countries. In the US, other heparin suppliers have issued precautionary recalls, and some medical devices makers have also recalled heparin-coated products.

In March, the FDA confirmed that it had found oversulfated chondroitin sulfate in samples of the active ingredient used in Baxter heparin. The FDA said the chondroitin sulfate was molecularly changed to mimic heparin’s blood-clotting properties. That ingredient was supplied to Baxter by Changzhou SPL, a Chinese plant partially owned by Wisconsin-based Scientific Protein Laboratories. It costs a fraction of the ingredient usually used in heparin, and producers may have used it in an attempt to cut costs.