Fourteen Chinese companies have been linked to contaminated heparin, an anticoagulant commonly used during surgical procedures and dialysis, according to a Wall Street Journal report.

The US Food and Drug Administration (FDA) added these companies to an import list allowing FDA to stop shipments at the border. That list already included eight other Chinese suppliers who were believe to have provided tainted raw materials for the making of heparin.

The Wall Street Journal reported the materials were delivered in 2008 and FDA doesn't have any evidence that the Chinese companies are currently supplying bad ingredients.

An estimated 12 million Americans use heparin each year, according to the report.

Read more:
The Wall Street Journal: Suppliers Linked to Impure Heparin
The New York Times: F.D.A. Lists Sources of Tainted Drug