In letters sent today, three Senators criticized controversial research apps used by Facebook and Google. The letters questioned the companies on the scope of their research, and asked Apple questions about how the company polices its App Store.

Last week, TechCrunch revealed that Facebook was paying people between the ages of 13 and 25 up to $20 a month to install an invasive research app that logged phone data. Soon after, the outlet noted similar activity from Google, and in response, Apple banned the internal iOS apps used by both companies until they came into compliance with Apple’s policies.

The letters sent today come from Senators Richard Blumenthal (D-CT), Edward Markey (D-MA), and Josh Hawley (R-MO), and are addressed to Facebook CEO Mark Zuckerberg, Google senior vice president of platforms and ecosystems Hiroshi Lockheimer, and Apple CEO Tim Cook.

Letters say news stories “fit with longstanding concerns” about Facebook

The letters say the news stories “fit with longstanding concerns that Facebook has used its products to deeply intrude into personal privacy,” and ask Facebook and Google for details on the research apps. In the letter to Zuckerberg, the senators ask when the project began, how many participants were under 18 years old, and exactly how data was collected and retained. The letters also question Google about its Google Play Store policies, as well as Apple on whether it has done a proactive search for similar apps.

The three companies did not immediately respond to a request for comment. The senators are requesting answers by March 1st.

The letters make clear the senators are looking at the potential for regulation in the future. “In light of recent invasions of children’s and teens’ privacy, including those described above,” the senators ask in their last question to Zuckerberg, “would Facebook support federal legislation to create new privacy safeguards for children and teens online?”