The blood-thinning drug heparin has been recalled after being linked to four deaths (and a current investigation into 17 additional deaths) and hundreds of reported cases of adverse reactions, including vomiting, labored breathing, and dangerously low blood pressure.

The drug itself is derived from pig intestines and has been used in dialysis and heart procedures to avoid blood clots in lungs, veins, and arteries.

Baxter International Inc., the drug company behind heparin, is currently under investigation by the FDA because of reported "objectionable conditions" that were discovered at the Chinese factory that supplied its raw ingredients. However, whether the Chinese plant is the cause of the problems remains unknown at this time, say FDA officials.