Five women who took the abortion pill RU-486 have died from bacterial infections since its U.S. introduction nearly five years ago, the manufacturer reported on Monday.

“No causal relationship between these events” has been established with the drug, also known as Mifeprex or mifepristone, maker Danco Laboratories LLC said.

“Childbirth, menstruation and abortion, whether spontaneous, surgical or medical, all create conditions that can result in serious and sometimes fatal infection, and there is no evidence that Mifeprex and misoprostol present a special risk of infection,” the company said in a statement.

Misoprostol is a drug that women must take two days after Mifeprex to complete the abortion.

Danco said it was sending a letter to alert physicians about the cases and updating warning information on the drug’s label.

Mifeprex already carries a warning about the possibility that women who take the drug could experience serious and sometimes fatal infections. The company is updating the label to give physicians more information to help them spot the problem, Danco spokeswoman Cynthia Summers said.

“With these very rare infections, we want people to be able to recognize them early,” she said.

RU-486 is approved for terminating a pregnancy of 49 days or less. Abortion opponents fought vigorously to keep it off the U.S. market and have asked the FDA to revoke the approval.

More than 460,000 U.S. women have taken Mifeprex since September 2000, Danco said.

One of the deaths occurred during a clinical trial in Canada in 2001, the company said. The other four were reported in California. Two of the California deaths were reported in late 2003, one in early 2004 and one in mid-2005.

Three of the cases involved a rare bacterium known as Clostridium sordellii, Danco’s statement said.

Women who take Mifeprex and misoprostol should contact a doctor or visit an emergency room immediately if they experience abdominal pain or discomfort or general malaise more than 24 hours after taking misoprostol, Danco said.