The Colorado Secretary of State’s office says it received notice Friday from the Department of Homeland Security that its elections systems were scanned for weaknesses in the weeks before the 2016 election.

The government told The Associated Press last year that more than 20 states were targeted by hackers believed to be Russian agents before the 2016 elections. But for many states, Friday's calls from DHS were the first official confirmation that they were on the list.

Federal officials said that in most of the 21 targeted states, the activity was limited, such as scanning computer systems. The targets included voter registration systems but not vote tallying software. Officials said there were some attempts to compromise networks but most were unsuccessful.

“According to Homeland Security, we were not attacked, probed, breached, infiltrated or penetrated,” Secretary of State Wayne Williams said in a statement on Friday. “This was a scan and many computer systems are regularly scanned. It happens hundreds if not thousands of times per day.

That's in line with a statement Williams made to CPR News in June, in which he said, "we're confident no election anywhere in this state were altered in any fashion. And we're confident that the voter registration system was not altered in any fashion as well."

Friday's disclosure to the states comes as a special counsel probes whether there was any coordination during the 2016 presidential campaign between Russia and associates of Donald Trump.

Trump, a Republican who defeated Democrat Hillary Clinton in the presidential election, has called the Russia story a hoax. He says Russian President Vladimir Putin "vehemently denied" the conclusions of American intelligence agencies.