New documents obtained through Freedom of Information requests reveal the widespread use of so-called stingray surveillance devices in California. The outlet Sacramento News10 obtained the documents, which were highlighted by the American Civil Liberties Union (ACLU).

Local law enforcement agencies across the Bay Area are using these devices, which mimics cell phone towers by tricking wireless tools on the same network and making the tools communicate with the stingray device. These devices are used in a dragnet fashion, collecting data about innocent third parties not the subject of any investigation. Additionally, it can pinpoint investigation targets with extreme precision. In total, nine law enforcement agencies in the state are using stingrays or recently obtained grants to use them, according to News10.

“Terrorism is used as the primary justification for purchasing StingRay technology in every grant application obtained by News10,” reporters Michael Bott and Thom Jensen write. “However, arrest records from Oakland and Los Angeles show that StingRays are being used for routine police work.”

In an analysis of the documents, the ACLU’s Linda Lye said the use of stingrays have troubling implications. “The acquisition of these devices is shrouded in secrecy and driven by federal grant money, which undermines local democratic oversight,” writes Lye. “There is a real question as to whether stingrays can ever be used in a constitutional fashion. They are the electronic equivalent of dragnet ‘general searches’ prohibited by the Fourth Amendment.”

The ACLU says it’s unclear whether stingrays can be used constitutionally. The group emphasizes that there needs to be transparency about how they can be used, like whether they are seeking court authorization to use them for investigations.

The police departments using stingrays are far from transparent, though. News10 was unsuccessful in getting any of the police agencies to comment in detail about their use of stingrays.