According to a new report, the voices of U.S. prison inmates are being recorded to build a voice recognition database.

The voice recognition technology is reportedly being used to cull information from the speaker’s voice for the purpose of digitizing that information to devise a unique and identifiable biometric signature called a voice print. Once captured, in some cases, reportedly, without the prisoner’s knowledge as they speak on the phone, the voice print is held in an incarcerated-persons' database. Using the database enables the prison to sort through past recorded conversations using algorithms to look for a specific voice and to flag conversations of a suspicious nature.

First developed with funding from the Department of Defense, the technology was originally intended to track terrorist activity. However, it was eventually sold to U.S. prisons and it is reportedly being used in prisons in New York, Texas, Florida, Arkansas and Arizona. It is estimated that roughly 200,000 voice prints of incarcerated people currently make up the database along with the voice recordings of those calling into the prisons to speak to an incarcerated friend or loved one.

Although there are reports suggesting that prisoners are unaware that they are being recorded, an inmate in New York’s Sing Sing prison alleges that he was coerced into participating with threats made about revoking his phone privileges. The inmate agreed to have his voice recorded as he listened for and repeated pre-recorded prompts into a phone.

Authorities and prison technology companies claim the voice recognition surveillance helps to support prison security and prevent fraud, however, civil liberties advocates are expressing concern about the lack of transparency and the alleged coercion used to ensnare participants of the program. Likewise, advocates are alarmed that the voices of those calling in are also subject to recording.

“Why am I giving up my rights because I’m receiving a call from somebody who has been convicted of a crime?” asked Jerome Greco, a digital forensics attorney at New York’s Legal Aid Society. Greco suggests that capturing the voice prints of outside parties should require a warrant. “If you have a family member convicted of a crime, yet you haven’t been, why are you now having your information being used for government investigations?”

Additionally, prisoner advocates also fear that such technology could derail prison organizing efforts.

“Using this technology to trace the voices of outside callers and flag those who speak with more than one person in a system, staff can use calls with outside organizers to quickly identify the incarcerated activist they support,” said Bianca Tylek, director of the Corrections Accountability Project, which works to prevent the influence of commercial interests in the criminal justice system.

The original report appears in The Intercept.