The predictive intelligence program has resulted in people being stopped, searched and in some cases arrested. A network of cameras scans and records vehicle license plate information, and an algorithm flags vehicles deemed suspicious based on where they came from, where they were going and which route they took. Federal agents in turn may then flag local law enforcement.

Suddenly, drivers find themselves pulled over — often for reasons cited such as speeding, failure to signal, the wrong window tint or even a dangling air freshener blocking the view. They are then aggressively questioned and searched, with no inkling that the roads they drove put them on law enforcement's radar.

Once limited to policing the nation's boundaries, the Border Patrol has built a surveillance system stretching into the country's interior that can monitor ordinary Americans' daily actions and connections for anomalies instead of simply targeting wanted suspects. Started about a decade ago to fight illegal border-related activities and the trafficking of both drugs and people, it has expanded over the past five years.

The Border Patrol has recently grown even more powerful through collaborations with other agencies, drawing information from license plate readers nationwide run by the Drug Enforcement Administration, private companies and, increasingly, local law enforcement programs funded through federal grants. Texas law enforcement agencies have asked Border Patrol to use facial recognition to identify drivers, documents show.

This active role beyond the borders is part of the quiet transformation of its parent agency, U.S. Customs and Border Protection, into something more akin to a domestic intelligence operation. Under the Trump administration's heightened immigration enforcement efforts, CBP is now poised to get more than $2.7 billion to build out border surveillance systems such as the license plate reader program by layering in artificial intelligence and other emerging technologies.

The result is a mass surveillance network with a particularly American focus: cars.

This investigation, the first to reveal details of how the program works on America's roads, is based on interviews with eight former government officials with direct knowledge of the program who spoke on the condition of anonymity because they weren't authorized to speak to the media, as well as dozens of federal, state and local officials, attorneys and privacy experts. The AP also reviewed thousands of pages of court and government documents, state grant and law enforcement data, and arrest reports.