The U.S. Food and Drug Administration (FDA) is investigating a website that recently began providing women in the United States with low-cost medication to cause early abortion at a relatively low cost.  The federal agency says that selling the pills online is illegal and breaks federal protocol, and anti-choice advocates are considering asking the U.S. Congress to step in as well.

The website Aid Access began selling drugs online this year, allowing people up to 10 weeks’ gestation to terminate their pregnancies for less than $100—one-fifth of the average cost of the same medication at a clinic.

Women in the United States are able to end first-trimester pregnancies at home with Mifeprex; also known as mifepristone, the drug prevents a pregnancy from continuing by blocking the hormone progesterone, dislodging an egg from the lining of the uterus. Another drug, misoprostol, “enhances contractions and helps to expel the products of conception from the uterus,” according to Aid Access.

The FDA has determined that Mifeprex, should only be “dispensed in certain health care settings, specifically, clinics, medical offices and hospitals, by or under the supervision of a certified prescriber. Mifepristone, including Mifeprex, for termination of pregnancy, is not legally available over the Internet,” the FDA said in an emailed statement to Rewire.News.

“The agency takes the allegations related to the sale of mifepristone in the U.S. through online distribution channels very seriously and is evaluating the allegations to assess potential violations of U.S. law,” the FDA said.

According to FDA guidelines, doctors must dispense mifepristone at clinics, medical offices, or hospitals. Aid Access uses a doctor to write prescriptions for the drug online, and distributes the drugs through the mail.

The FDA also posted a notice online warning consumers not to by Mifeprex over the internet “because you will bypass important safeguards designed to protect your health (and the health of others).” Drugs that are “purchased from foreign Internet sources are not the FDA-approved versions of the drugs, and they are not subject to FDA-regulated manufacturing controls or FDA inspection of manufacturing facilities,” the agency warned.

But not everyone agrees. Major medical organizations and physicians have argued that the drugs should be more widely available and are perfectly safe for home use. Experts have argued in the Journal of the American Pharmacists Association that the limitation is not warranted, and medication abortion up to 10 weeks’ gestation is the safe, effective, and preferred method for terminating a pregnancy. Pharmacists can dispense the medications upon a doctor’s prescription in Australia and some provinces of Canada, the commentary said.

“This restriction might have made sense when mifepristone was first approved in 2000, given the limited safety data from the US at that time, But after 18 years of evidence of the drug’s safety, this is no longer needed. Canada recently approved mifepristone, and the drug is already available at pharmacies by prescription,” said Dr. Daniel Grossman, director of Advancing New Standards in Reproductive Health (ANSIRH), a research center at the University of California, San Francisco.

Aid Access responded to questions about the investigation by referring Rewire.News to a recent publication by the Guttmacher Institute, an abortion research and policy institution, arguing that the FDA restrictions on mifepristone “are not justified.” It cites support for lifting restrictions from the American Medical Association and the American College of Obstetricians and Gynecologists. The “limits imposed on mifepristone are both burdensome on those seeking to access medication abortion and ineffective in addressing any risks associated with the medication,” the Guttmacher Institute said.

The founder of Aid Access, Dr. Rebecca Gomperts, has offered similar services in countries where abortion is illegal through her site Women on the Web. Aid Access reportedly launched in April and has since received thousands of requests. Gomperts was not made available for an interview with Rewire.News.

While medication abortion is generally available in the United States, access to abortion providers varies widely. Women in 27 large U.S. cities would have to travel more than 100 miles each way to access abortion services, according to ANSIRH research. Six states have just one abortion-providing facility.

Medication abortions have risen in recent years—from 6 percent of non-hospital abortions in 2001 to 31 percent in 2014. That is despite a decline in the overall rate of abortion: The abortion rate in 2014 was lower than it was when abortion became legal in 1973, according to the Guttmacher Institute.

Anti-choice advocates have vowed to fight Aid Access’ work and are now considering advocating for Congress to intervene. Americans United for Life (AUL) President Catherine Glenn Foster said in a statement that the service is “reckless and irresponsible” because no ultrasound is performed, and thus it is not possible to know if the pregnancy is ectopic.  “Because Gomperts’ plan is dangerous to women’s health and safety, the act of sending unregulated prescription abortion pills through the mail should be the subject of federal regulation,” Foster said.

“Research has shown that women who know when their last period started are generally accurate at determining how far along they are in the pregnancy,” Grossman argued in response. “These medications are not thought to be effective to treat an ectopic pregnancy, but they won’t make the complications from an ectopic worse. Ectopic pregnancy is very rare—and apparently rarer among women seeking abortion compared to the general population. Most women with an ectopic will have unusual symptoms like pain or bleeding, and they should be advised to seek care.”

A spokesman for the Republican-led House Energy and Commerce Committee did not respond to questions about whether the committee is considering an investigation.

AUL may already have an inside track at the FDA and its parent agency, the U.S. Department of Health and Human Services. The department’s assistant secretary for public affairs is Charmaine Yoest, the former president of AUL.