WASHINGTON (AP) -- An abortion pill implicated in the death of an 18-year-old California woman last fall will add new warnings linking RU-486 to the risk of serious bacterial infection.

Holly Patterson died Sept. 17, 2003, of septic shock caused by inflammation of the uterus. The teen died weeks after taking RU-486 to terminate an unplanned pregnancy. Anti-abortion activists seized upon her death in their campaign against these pills, including Danco Laboratories' product, Mifeprex.

The Food and Drug Administration approved Mifeprex in 2000 to terminate pregnancy up to 49 days after the beginning of the last menstrual cycle. The drug blocks progesterone, a hormone required to sustain a pregnancy. When followed by another medicine, misoprostol, Mifeprex terminates the pregnancy.

Mifeprex already carries a black box warning, the agency's most strident alert, to highlight other safety concerns. The FDA said Monday that the drug's black box warning will expand, adding information about the such rare but potentially life-threatening complications as serious bacterial infections and bleeding that can follow any abortion, including one induced by Mifeprex.

Since the drug was approved, the agency has received reports of serious bacterial infection, bleeding, ectopic pregnancies that have ruptured and death. The fatalities including a death from sepsis, a severe infection, recently reported to FDA, leading to the revised black box.

Serious bacterial infection may happen silently, without fever or tenderness -- typical signs of infection - the label warns. The revised label also cautions health care providers that prolonged, heavy bleeding may warrant surgical intervention.

Women who have taken the drug should contact a doctor immediately if they suffer fever, abdominal pain and heavy bleeding, a medication guide aimed at consumers says. And the FDA counsels women to take their medication guide to any health care provider they visit to speed treatment.

Danco Laboratories did not immediately return a phone call seeking comment. In an earlier statement, the company said 200,000 American women and more than 1 million women worldwide have used the pill since it was invented in France in the 1980s.

Concerned Women for America blasted the FDA for not pulling RU-486 from the market.

"It is reported that another woman has died after taking the abortion drug RU-486, and the FDA's response is to change the drug's label," Wendy Wright, the group's senior policy director, said in a statement. "This is a dangerous drug that deserves to be pulled off the market immediately."

The agency said it would continue to monitor the drug and may take further action.

At least two other American women who took the pill in the United States died, although the FDA says it is unclear if their deaths were directly related to the pill's use.

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