(LM Otero/AP)

Immigration agents have been tapping into a vast, privately maintained database of license plate numbers gleaned from vehicles across the United States to track down people who may be in the country illegally, according to documents obtained by the American Civil Liberties Union and released Wednesday.

The database contains billions of records on vehicle locations captured from red-light and speed-limit cameras as well as from parking lots and toll roads that use the nearly ubiquitous and inexpensive scanners to monitor vehicle comings and goings.

Local police forces have long used those scanners to track criminal suspects and enforce traffic laws across the United States. But the records the ACLU obtained from the Department of Homeland Security through a Freedom of Information Act request shed new light on a little-noticed and expanding network of surveillance that has developed over the years and for which there appear to be few legal limitations.

The revelation drew sharp criticism from Democratic Sen. Ron Wyden of Oregon, who said the mere notion of “a massive, for-profit location-tracking database is about the worst idea I have ever heard of when it comes to Americans’ privacy and security.”

“There needs to be strong rules around how sensitive data like this is stored and controlled – location data of millions of Americans is a ripe target for predators, domestic abusers, and foreign spies,” he said in a statement.

Immigration and Customs Enforcement’s use of some of the information in states including California also appears to skirt limitations that “sanctuary cities” have placed on police cooperation with the immigration agency, the ACLU said.

“The ACLU’s grave concerns about the civil liberties risks of license plate readers take on greater urgency as this surveillance information fuels ICE’s deportation machine,” said Vasudha Talla, a staff attorney with the ACLU of Northern California, in a blog post.

Talla wrote that the “information is stored for years, generating a literal and intimate roadmap of people’s private lives,” and stressed the data show that cities and states need to adopt tougher rules governing when, and how, license-plate scans should be used.

ICE spokesman Matthew Bourke said that agents use the license-plate database as a tool to help in its immigration-enforcement investigations and that it does not use the information to track people “who have no connection to ICE investigatory or enforcement activities.”

Bourke said ICE agents are required to undergo yearly data-security and privacy training and that the agency allows employees to access the data only for “mission-related purposes.” ICE said the California company that maintains the database, Vigilant Solutions, is required to notify ICE if it spots unauthorized uses, and that ICE can request audits in case of potential abuse.

Mounted on police squad cars and above major roads, the scanners automatically log the time, location and license plate of all cars that pass by, filling out a database law-enforcement authorities could use to precisely monitor a person’s travels, according to the ACLU.

The database contains years of data about vehicles on American roads and tracks not only traffic violators, but any car that passes a bridge, tow truck or parking garage where the cameras are in use.

That’s become a valuable trove for ICE, which has been able to access driver-location information culled from businesses in America’s 50 biggest metropolitan areas, the ACLU records show. Thousands of ICE employees, including some who work on deportation cases, have access to the database, the watchdog group said.

ICE agents also appeared to have access to data voluntarily shared by dozens of local police agencies across the United States, even in places that have policies limiting police cooperation with ICE. More than 80 local law-enforcement agencies across California, Texas and other states that also use the system appear to have chosen to make their data available to ICE, according to a report unearthed by the ACLU.

Among them appear to be sanctuary cities that generally refuse to help with federal deportation efforts, such as Union City, Calif., according to a report included in the documents. A file dated August 2008 included Union City on a list of law-enforcement agencies from which ICE had been “receiving detection data."

The ACLU said it is unclear if local residents had been aware of the relationship, and they argued it amounted to a violation of state law, which prohibits California police agencies from cooperating with ICE.

In response, however, Union City said in a statement that its police department does not “own or operate” license-plate readers, that “there is no license plate information provided" to the Vigilant database, and that it does not share information with ICE. The city said it would seek further information about the license-plate program.

Also on the list is the Austin Police Department, where city leaders have passed resolutions restricting police officers’ ability to ask people about their immigration status. Those measures were passed in opposition of Texas’ “anti-sanctuary city” law, which has been challenged in federal court but remains in effect. An Austin police representative said that state law prevents the department from adopting any rules that would prevent its officers from sharing information with ICE.

In some cases, emails unearthed by the ACLU show ICE agents asking seemingly friendly local law-enforcement officials for access to license-plate data they may not have been able to see otherwise.

In one internal document, an ICE official says not having access to a license-plate database would “severely limit” agents’ ability to find and apprehend targets, saying “the arrest rate would decline by as much as 20%.” The document offers no detail on how ICE calculated that possible decline.

ICE signed a $6 million contract with Vigilant in 2017. The agency announced at the time that it would use it to support “criminal and administrative law enforcement missions.”

Some ICE field agents had been using such a system for years, despite longtime objections from consumer-protection advocates and lawmakers in Congress. Homeland Security itself had scrapped a plan in 2014 to develop a national license-plate tracking database in response to privacy concerns.

Vigilant says its database has more than 5 billion nationwide license-plate “detections” and adds another 150 million every month. Officers can search for a license plate to find everywhere that car was seen on camera, or get alerted whenever the license plate is spotted.

The documents include emails in which ICE agents asked police officers to hand over driver information from the database to help investigate specific targets. ICE’s privacy rules say that license-plate data searches may be used for authorized criminal law-enforcement purposes, including removing “criminal aliens, fugitive aliens (and) illegal reentrants.”

Critics say the system subjects innocent people to an improper level of government surveillance, because the scanners log license-plate data on every passing car, and not just those owned by criminal suspects. Unlike GPS-tracking devices that police must get warrants to legally use, officers can access years of data without getting permission from a judge.

“ICE has long embraced technology to target immigrants,” the ACLU’s Talla said in the blog post. “Now it’s taking surveillance to an unprecedented level to target vulnerable communities — and sweeping up everyone else in the process.”