CHICAGO – The U.S. Food and Drug Administration said Friday that it will stop and test all heparin products slated for import in the U.S. as part of its widening investigation into the cause of hundreds of allergic reactions related to a similar blood thinner sold by Deerfield, Ill.-based Baxter International Inc.

The FDA said it has found a “heparin-like” contaminate in 20 of 28 samples of heparin’s active pharmaceutical ingredient tested in batches made by Baxter’s supplier, Wisconsin-based Scientific Protein Laboratories at its plant in China. The FDA still said it has not found the cause of the more than 700 allergic reactions that have been linked to at least four deaths.

“There is now a worldwide testing effort going on,” said Dr. Janet Woodcock, director of the FDA’s Center for Drug Evaluation and Research.

The FDA’s inspection team has visited so-called “consolidators,” who acquire raw heparin, produced from the mucous lining of pig intestines, from numerous farms. However, the inspectors have not visited any farms and do not plan to do so, officials said. Instead, the FDA is asking Chinese authorities to send agricultural inspectors to the farms.

Scientific Protein provided Baxter with heparin’s active ingredient before Scientific Protein’s plant in China was shuttered last month amid an investigation into hundreds of life-threatening allergic reactions and at least four deaths.

Allergic reactions, which include racing heartbeats and low blood pressure, have been linked to China-sourced heparin made by Scientific Protein in Germany and the U.S.