(CNSNews.com) - Two women taking RU-486, the abortion-inducing drug combination, have died, the drug maker says, and four others have become very ill. According to a report in Thursday's Washington Post, Danco Laboratories, the maker of the drug marketed as Mifeprex, has sent a letter to doctors, telling them about the six women. The letter, however, also says it's not known if RU-486 actually caused the deaths and illnesses. According to the newspaper report, three women suffered bleeding caused by the rupture of ectopic (fallopian tube) pregnancies; one died. Two other women had serious bacterial infections; one of them died. The sixth patient had a heart attack three days after taking RU-486, but she recovered. The letter Danco sent to doctors reminded them to report any serious problems in women who take the abortion drug. The FDA approved RU-486 as an abortion-inducer in September 2000, and at the time, pro-life groups warned of its dangers.