Immigration and Customs Enforcement has been using powerful technology to track where people are driving, documents released on Wednesday show.

The documents were obtained and released by the American Civil Liberties Union on Wednesday, and show that more than 9,200 ICE employees have been using a database tracking automated license plate readers across the US.

Agencies like ICE are continuing to rely on surveillance technology, as a federal spending bill looks to provide $100 million to fund border surveillance tech. Tech giants like Amazon and Microsoft have also offered technology like facial recognition to ICE.

The technology allows ICE to target people on a massive scale, and is widely considered as an invasion of privacy by advocate groups. Privacy concerns with technology have grown as software shows it's capable of tracking people's every move, with or without their consent.

In China, surveillance technology is being used to monitor citizens and assign social credit scores, which can lead to civil penalties.

The database ICE uses contains more than 5 billion points of location data, collected by license plate readers in parking lots, on roads, toll booths and police cars, the ACLU said. This data is collected on every license plate that passes a reader -- meaning that innocent people just traveling on their daily commutes have their movements captured and viewed by ICE on a regular basis.

An additional 1.5 billion license plate data points came from over 80 local police departments in dozens of states, the documents showed. The ACLU said that this mass surveillance violates local privacy laws, as local government agencies are handing over that data willingly to ICE. 

"Storing that much location information is both a significant invasion of privacy and entirely unnecessary to find someone's current location," Vasudha Talla, the ACLU of Northern California's staff attorney, said in a post on Wednesday.

The database adds an additional 150-200 million new license plate scans every month, according to documents the ACLU obtained. These automated license plate readers can photograph thousands of plates a minute.

The data comes from Vigilant Solutions, a company that ICE started working with in 2018 with a $6.1 million contract set to expire in 2020. The company boasts that it has license plate data from about 60 percent of the US population, including areas like New York, Los Angeles, Chicago, Atlanta, San Francisco, Cleveland and Austin.

A key part of the data collection was requesting the information from local police department. Vigilant's documents included a step-by-step guide on how to befriend officers and request location data from local police.

ICE has privacy rules that require all use of license plate data to be documented requests. But logs obtained by the ACLU show that these requests were often informal, provided through emails that work around that process.

The ACLU is calling on local law enforcement to stop sharing people's information with ICE.

"It is appalling that ICE has added this mass surveillance database to its arsenal, and that local law enforcement agencies and private companies are aiding the agency in its surveillance efforts," Talla said in a statement.