Want to know how federal law enforcement uses facial recognition? Tough luck.

A report by the Government Accountability Office this week revealed that 20 agencies have worked with this technology, which analyzes photographs of faces and matches them to other photographs by algorithm. Of those 20, however, 13 couldn’t say precisely what systems they had used — the agencies were essentially borrowing tools owned by other federal, state, local and even private entities containing millions or billions of photos without keeping tabs. The news is especially alarming given the array of agencies using the tools, including those not traditionally associated with law enforcement, for an array of activities, including those besides criminal investigation.