Sen. Elizabeth Warren (D-Mass.) led 13 other Democratic senators on Wednesday in blasting data brokers for collecting and selling the cellphone-based location data of people who visit abortion clinics, saying the companies are risking those people’s safety.

In a letter to companies SafeGraph and Placer.ai, the senators demanded answers about the data brokers’ collection practices and called on them to create a complete and permanent ban on those and similar practices.

“Anti-abortion activists have already used location data to send targeted anti-choice ads to women’s phones while they are sitting in abortion clinics,” the senators wrote in the letter. “Anti-abortion politicians in Republican-led states have placed bounties on women who receive abortions and doctors that provide them and even proposed laws that would punish pregnant people for traveling to seek abortions out of state. Anti-abortion prosecutors have used search and message data to criminally charge abortion-seekers.”

Data brokers in the U.S. typically use a three-step business model, according to the senators. Companies first collect a variety of data from Americans when they use web and mobile applications, often without their informed consent. Data brokers then repackage that data and sell it in bulk to purchasers who buy the data for a variety of purposes, making what the senators said is a $200 billion data broker industry incredibly profitable.

But according to the senators, SafeGraph and Placer.ai specifically collect precise location and time data, revealing the locations of people at abortion clinics before, during and after their visits — including where they live.

“These and other practices targeting women seeking necessary health care services are almost certain to escalate if Roe v. Wade is gutted and abortion is criminalized instantly in states across the nation,” the senators wrote. “Under these circumstances, [your company’s] decision to sell data that allowed any buying customer to determine the locations of people seeking abortion services was simply unconscionable, risking the safety and security of women everywhere.”

SafeGraph told HuffPost that the company does not provide any data about any individuals — only physical places — and maintained that its customers cannot deanonymize the data. The company also rejected a claim in the senators’ letter that Google had banned SafeGraph, saying the tech giant had never contacted the data broker.

The company also pointed to a May 3 statement saying it is removing datasets that show how groups of people interact with “family planning centers,” but will continue providing data on such places that include their location and hours.

However, the senators said that SafeGraph has still not offered details about how many Americans’ data it sold, who purchased it, how long it was publicly available, whether the data removal was permanent and what SafeGraph would do to support those whose data had already been sold.

Placer.ai declined to comment specifically on the senators’ letter, but referred to a May 6 statement the company made saying it never has and never will sell user-level data, and “deliberately” does not participate in the “ad tech industry where most customers expect to be able to track individual behavior.”

“Following recent media reports, we removed all Planned Parenthood locations from our dashboards – the only abortion provider in our system – to dispel any potential concerns about how our data can be used,” the statement read. “Additionally, our team confirmed that there were no searches for Planned Parenthood on the Placer system prior to these specific media inquiries. This is a part of an ongoing effort to remove all sensitive places from our system.”

Federal Trade Commission Chair Lina Khan spoke about location tracking at a House Appropriations Committee hearing on Wednesday. Khan said the commission is taking a “comprehensive approach” to deterring unlawful data practices, including those that harm user privacy or data security.

“It is enormously concerning the degree to which we’ve seen tracking of people’s location basically emerge into a very lucrative market where all sorts of companies ranging from data brokers to aggregators are now trafficking in this data, which as you noted can be extremely informative and insightful,” Khan said to Rep. Norma Torres (D-Calif.), who asked about the issue.

“It can tell you when people are going to church, if they’re accessing reproductive health services, and can be exploited by a whole set of bad actors. So this is certainly something that is on the FTC’s radar; the FTC in the past has done workshops and enforcement actions in this area.”

Khan cited the FTC’s action against “stalkerware” company SpyFone, which allegedly sold software that allowed purchasers — potentially including stalkers — to monitor another person’s phone and have real-time access to sensitive activity. The commission banned both the company and its CEO from the surveillance business, but Khan acknowledged the current data broker market is even more troubling.

“I think the fact that we have an entire sub-economy on this that’s incentivizing the endless collection of this data, even if the app or service doesn’t require your location – I think that invites us to think hard about whether we need to be setting clear limits on this type of thing,” she said. “And of course, there are a lot of discussions in Congress around potential privacy legislation.”

Read the senators’ full letters below.