A license-plate tracking system originally conceived to combat drug traffickers along the U.S.-Mexican border has drastically expanded to encompass millions of vehicles across the United States, according to official documents released Tuesday.

Law enforcement officials have tapped a database of vehicle movements, including times, dates and in some cases, images of drivers snapped by roadside traffic cameras, the Wall Street Journal reports.

The Drug Enforcement Agency established the program to monitor and impound cars used by drug traffickers along the US-Mexico border, but documents obtained by the Wall Street Journal suggest that the program has expanded for a range of investigations unrelated to drug trafficking cases. Sen. Patrick Leahy criticized the unpublicized expansion of the program, saying that it “raises significant privacy concerns.”

Read more at the Wall Street Journal.

Get The Brief. Sign up to receive the top stories you need to know right now. Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Contact us at letters@time.com.