The Department of Homeland Security notified 21 states Friday that Russian hackers attempted unsuccessfully to interfere with their voting systems in the 2016 election.

DHS reported that no votes were changed by Russian hacking, Reuters reports. DHS refused to disclose which state governments it approached, but Wisconsin officials made it known that they were among the group.

Wisconsin Elections Commission Administrator Michael Haas said that he was informed that "Russian government cyber actors" targeted his state's voter registration systems.

Russian hackers "scanned internet-connected election infrastructure likely seeking specific vulnerabilities such as access to voter registration databases, but the attempt to exploit vulnerabilities was unsuccessful," Haas said.

In June, DHS informed Congress that 21 states were targeted by hackers, but that while a few were breached, no votes were changes.

Wisconsin was a decisive state in the 2016 presidential election, casting its 10 electoral votes for Republican nominee Donald Trump for its first time backing a Republican since 1984. In the wake of the election, several analyses pointed to Democrat Hillary Clinton's failure to visit Wisconsin as a major blunder during the campaign.