The U.S. government individually called election officials in 21 states on Friday afternoon to inform them their systems had been targeted by Russian hackers trying to impact the U.S. presidential election last year.

The Department of Homeland Security initially revealed the breaches at a hearing in June, but the agency hadn’t revealed exactly who had been targeted. The DHS has not publicly disclosed what the hackers were trying to achieve or who they were working for, but officials from multiple states confirmed they were notified of Russian involvement.

Wisconsin’s Elections Commission issued a statement saying it had been notified that “Russian government cyber actors” had to tried to target its voter registration system, but that they were unsuccessful.

The Associated Press also confirmed so far that Alabama, Arizona, Colorado, Connecticut, Illinois, Iowa, Maryland, Minnesota, Ohio, Oklahoma, Pennsylvania, Virginia, Washington and Wisconsin were targeted.

Politicians in Washington expressed anger at how long it took for Homeland Security to notify the states, and called for stronger, more sophisticated election systems to block future cyber attacks.

Democratic Sen. Mark Warner of Virginia, who is the vice chairman of the Senate Intelligence Committee, issued a statement calling it “unacceptable that it took almost a year after the election to notify states that their elections systems were targeted.”

Democratic Rep. Adam Schiff of California, the ranking member of the House Intelligence Committee, also tweeted that the Department of Homeland security should “notify states of attempted election hacking in real time, not a year later.”