Lawmakers are looking to question Facebook about its privacy practices after allegations that the service revealed sensitive health information in groups.

In a Federal Trade Commission complaint, filed last month and publicly released yesterday, a security researcher and health advocates said the company was failing to keep sensitive data secure. The complaint stemmed from an incident last year, when members of a group for women with a gene mutation called BRCA learned that information like names and email addresses could be accessed from “closed” groups.

Facebook has since removed the ability to harvest that information, but it has denied that there was ever a security loophole, and has pointed to the option to create less discoverable “secret” groups. The complaint argued that, despite the change, personal information is still too accessible by people within sensitive groups.

Questions whether Facebook “potentially misled” users

Now, a letter from lawmakers on the House Committee on Energy and Commerce is questioning whether Facebook users were “potentially misled” about what data they would reveal by joining a closed group. The letter, addressed to Mark Zuckerberg, questions whether the company “may have failed to properly notify group members that their personal health information may have been accessed by health insurance companies and online bullies, among others.” The letter requests a staff briefing about the issues raised in the complaint.

"Facebook is not an anonymous platform; real-name identity is at the center of the experience and always has been," a Facebook spokesperson said in a statement. "It’s intentionally clear to people that when they join any group on Facebook, other members of that group can see that they are a part of that community, and can see the posts they choose to share with that community. There is value in being able to know who you’re having a conversation with in a group, and we look forward to briefing the committee on this."

The company is reportedly negotiating with the FTC over a potentially massive fine for privacy issues.

“In light of the Committee’s continuing commitment to protect the privacy of the American people, we request a staff briefing on the issues raised by the complaint no later than March 1, 2019,” the letter reads, “so we can better understand Facebook’s practices with respect to so-called closed and anonymous groups.”

Update, 8:55PM ET: Includes statement from Facebook spokesperson.