SIOUX FALLS, S.D. — The South Dakota chapter of the American Civil Liberties Union said it’s concerned about a report that the U.S. military is using high-altitude balloons to conduct surveillance tests in six Midwestern states.

There are reportedly up to 25 balloons being launched from South Dakota, and will drift through parts of Minnesota, Iowa, Wisconsin, Missouri and Illinois. Filings examined with the Federal Communications Commission say the balloons are meant to provide persistent surveillance to locate drug trafficking and homeland security threats.

The ACLU said this kind of constant surveillance violates the privacy of citizens, creating what’s a pervasive checkpoint over cities. The ACLU said the military needs to be clear about information it’s collecting.

A spokesman with the U.S. military didn’t immediately respond to an email from The Associated Press.