Three prominent U.S. senators sent a letter to Facebook, Google and Apple executives this week in the wake of a TechCrunch report detailing how Facebook used iOS and Android apps to monitor teen users. In their letter, the lawmakers grilled Facebook and the other companies for more details about the app and the info it collected from minors.

“These reports fit with long-standing concerns that Facebook has used its products to deeply intrude into personal privacy,” the letter read. The lawmakers demanded to know exactly what information Facebook has gathered from its young users and how the company uses that information. They also pressed all three companies on supporting legislation to protect the privacy of children and teens online.

For its part, Facebook strongly contested the notion that it was “spying” on users without their consent, and that these users consented to giving up their data while using the VPN app.

“Despite early reports, there was nothing ‘secret’ about this; it was literally called the Facebook Research App,” a Facebook spokesperson told TechCrunch. “It wasn’t ‘spying’ as all of the people who signed up to participate went through a clear on-boarding process asking for their permission and were paid to participate.”

The fact that politicians are already involved spells trouble for Facebook’s public image. However, these two other tech giants getting dragged in to the issue means there could be serious repercussions for the company’s business, too.