The FDA examined the wrong factory when assessing the safety of a Chinese-made ingredient used to make Baxter International’s blood thinner Heparin. The drug has been recently linked to four deaths and hundreds of reports of allergic reactions.

Investigators are slated to travel to China this week to inspect the factory that produces the drug’s main ingredient, said Joseph Famulare, deputy director of the Center for Drug Evaluation and Research’s compliance department. The Chinese manufacturer was not initially inspected because it was confused with another company in the agency’s database with a similar name, Famulare said in published reports.

As of now, the agency remains unsure as to what exactly is to blame for the deaths and allergic reactions associated with Heaprin.

Inspections are also under way at a Baxter facility in Cherry Hill, NJ, and at company supplier Scientific Protein Laboratories in Waunakee, WI.

Last week the FDA asked healthcare providers to stop using Heparin citing the side effects. In 2007, the FDA received 100 reports of problems with the drug.

Last month, Baxter recalled nine lots of Heparin after learning of allergic reactions among dialysis patients. Problems included dizziness, fainting, and racing heartbeat.