The Department of Homeland Security has put out a call to contractors for a National License Plate Recognition database, according to documents uncovered by Ars Technica. Once built, the program would knit together data from license plate scanners around the country, potentially allowing DHS authorities to track individual cars from city to city without leaving the central hub. Further details of the program remain unclear.

The American Civil Liberties Union has been raising alarms about license plate scanners for years, but this is the first indication that data from the scanners will be coordinated on a national level. A July 2013 report uncovered 25 separate jurisdictions using the scanners, including Boston, Washington DC, and the New Jersey State Police. In 2012, scanners in the DC area collected more than 200 million license-plate impressions, roughly 0.1 percent of which were related to particular targets.

Update: Hours after this post, the Department of Homeland Security's Immigration and Customs Enforcement division pulled down the documents and withdrew the request, The Washington Post reported.