A day after Apple unveiled its new iPhone X, which allows its owner to unlock the device using facial recognition – a US senator is pressing the tech giant to detail its privacy and security safeguards for biometric data.

Senator Al Franken in a letter to the company is concerned that Apple could use the so-called faceprints it collects through its new unlocking system, called Face ID, “to benefit other sectors of its business, sell it to third parties for surveillance purposes, or receive law enforcement requests to access it facial recognition system.”

Phil Schiller, Apple’s senior marketing VP, said facial-recognition data would be stored on individual iPhones, not sent to some cloud server operated by Apple.

Still, Franken wants to know how Apple might handle government requests for “faceprint data or the Face ID system itself.”