The Food and Drug Administration said it is investigating recent "serious adverse events," including deaths, associated with Mifeprex, better known as RU-486, the so-called "abortion pill."

There are now four cases of deaths from infection from September 2003 to June 2005 following medical abortion with the drug, the FDA said.

"The FDA is committed to sharing emerging drug information with the public and we believe it is important to share with healthcare providers and patients the latest serious reports of infection associated with this drug that we have received," said Dr. Steven Galson, Acting Director of FDA's Center for Drug Evaluation and Research.

The FDA's warning highlighted the risk of sepsis or blood infection when undergoing medical abortion using the drug in a manner that is not consistent with the approved labeling.

The bacteria thought to have caused the fatal infection have been identified in two of the cases and the other two cases are under investigation by FDA along with the Centers for Disease Control and Prevention, State and local health departments, and the manufacturer of Mifeprex.

Doctors are urged to have a higher level of suspicion for sepsis in their patients taking Mifeprex.

Previously, the FDA has received reports of serious bacterial infection, bleeding, ectopic pregnancies that have ruptured, and death. Those reports led to the revision of the black box labeling. Mifeprex was approved by the FDA in 2000.

The incident is "further evidence of the abortion industry's pursuit of a reckless path of destruction that leaves millions of victims dead in its wake," said Judie Brown, president of American Life League. "How many more women and preborn children must die before this lethal drug is taken off of the market?"