State police in Virginia recorded and collected the whereabouts of potentially millions of people in an effort to monitor attendees at political rallies in 2008 and 2009, according to Freedom of Information Act request filed by the Richmond Times-Dispatch.

The documents from the request show that police agencies used license plate readers in order to record information about people traveling to at least three politically-charged events during the 2008 presidential election season, including logging data for every vehicle leaving the state end route to Washington, DC for President Obama’s first inauguration ceremony and (three months prior) campaign rallies in Leesburg, Virginia, being held by then-candidate Obama and Sarah Palin, the Republican nominee for vice president, RT reports.

The U.S. Secret Service directed state police to use the readers to “capture and store the plate images as an extra level of security for the inauguration.” While it is estimated that 1.8 million people attended the event in late January 2009, the amount of data still on file is unknown.