The US government said on Thursday that batches of the recalled blood thinner heparin, which contained an unidentified contaminant that might have caused 19 deaths, were supplied fom China.
The federal Food and Drug Administration (FDA), which added that Germany has announced its own recall of heparin due to allergic reactions, has yet to prove that the contaminant was the cause of the deaths as well as other adverse health effects.
But the FDA said that all the US batches of heparin linked to health problems and deaths were made with ingredients that came from China.
'At this point, we do not know whether the introduction was accidental or whether it was deliberate,' said FDA deputy commissioner Janet Woodcock.
'We don't know if any of the heparin products worldwide might contain this contaminant and that is something we are going to be looking into.'
Magnetic resonance imagery (MRI) tests performed on the anti-coagulants showed that up to 20 percent of the active ingredient in the medication contained the unknown contaminant, the FDA said.
On February 11, the FDA announced a limited recall of Baxter International pharmaceuticals' multi-dose heparin and on February 28 the lab expanded the recall to include nearly all heparin being produced.
The injectable drug is made in part from pig intestines. Baxter's supplier, Scientific Protein Laboratories based in Wisconsin, sometimes buys the raw ingredients from unregulated shops in China, according to the New York Times.
However, Wayne Pines, a spokesman for Scientific Protein Laboratories said there was 'no evidence of counterfeiting or tampering or anything of that nature.'
'No one really knows what happened here,' he said.
The FDA has so far received 785 complaints of health problems as well as 46 reports of death, but Woodcock said that the FDA determined that only 19 of the deaths were linked to the drug. Baxter maintains that four people have died as a result of the drug.
The Times said that the FDA has admitted to violating 'its own policies by failing to inspect Scientific Protein's China plant before approving the drug for sale.'
FDA inspectors who visited a plant in Changzou that makes the drug components for US production found 'at least some heparin was made from 'material from an unacceptable workshop vendor.''