Two Russian nationals visited Colorado in 2014 as part of a larger effort to gather intelligence on swing states, undermine the U.S. political system and, eventually, support Donald Trump’s presidential candidacy, according to an indictment of 13 Russians released Friday by special counsel Robert Mueller.

The charging documents say the two were trying to get information on Colorado and other so-called purple states — which have a near-even mix of Democratic and Republican voters — as part of their research.

Colorado came into focus for the broader group of defendants, the indictment indicates, after they spoke with a person affiliated with a Texas-based grassroots organization who told them that they should center their activities on states like Colorado, Virginia and Florida.

The indictment also follows earlier reports of Russian-linked actors trying to digitally scan Colorado’s election system for weaknesses. Though it’s unclear whether the two are related, Friday’s revelation mark at least the second attempt by a foreign power to infiltrate or operate in the state surrounding the 2016 election.

The indictment — which also names a handful of companies linked to the Russians’ alleged activities — involves charges of conspiracy, wire fraud, bank fraud and aggravated identity theft. Generally, the group is accused of attempting “to sow discord in the U.S. political system, including the 2016 U.S. presidential election.”

“They engaged in operations primarily intended to communicate derogatory information about Hillary Clinton, to denigrate other candidates such as Ted Cruz and Marco Rubio, and to support Bernie Sanders and then-candidate Donald Trump,” the indictment says.

Those indicted allegedly tried to accomplish their goals through social media accounts and by advertisements and staging political rallies “while posing as U.S. grassroots entities and U.S. persons, and without revealing their Russian identities.”

Deputy Attorney General Rod Rosenstein told reporters at a news conference Friday that authorities don’t believe any Americans were willing participants in the Russians’ alleged plot and activities.

“The defendants allegedly conducted what they called ‘information warfare’ against the United States with the stated goal of spreading distrust toward the candidates and the political system in general,” Rosenstein said.

He added: “They used stolen or fictitious American identities, fraudulent bank accounts and false identification documents. The defendants posed as politically and socially active Americans, advocating for and against particular candidates.”

As for the Colorado connection, the indictment says that Anna Vladislavovna Bogacheva and Aleksandra Yuryevna Krylova traveled around the U.S. in June 2014, making stops in Nevada, California, New Mexico, Colorado, Illinois, Michigan, Louisiana, Texas and New York “to gather intelligence.”

The indictment does not go into detail about their alleged activities in Colorado.

Colorado election officials have said the state’s voting system may have been scanned for weakness by Russian-linked actors leading up to the 2016 election. The Colorado Secretary of State’s Office — which on Friday said it was reviewing the indictment — has previously said, however, that it doesn’t believe the state’s elections systems were breached or compromised.

“A reminder that this investigation should be of the utmost importance to all Americans, regardless of political party,” U.S. Rep. Diana DeGette, D-Denver, said in a statement. “Ensuring integrity of elections, preventing foreign interference and combating damaging trends in our civil discourse all are parts of preserving our democracy.”

The charges are the latest allegations arising from Mueller’s probe into Russian meddling in the 2016 election and represent the first criminal case against Russians.

Before Friday, four people, including Trump’s former national security adviser and former campaign chairman, had been charged.

In response to the indictment Friday, President Trump tweeted that his campaign “did nothing wrong — no collusion!”

Russia started their anti-US campaign in 2014, long before I announced that I would run for President. The results of the election were not impacted. The Trump campaign did nothing wrong – no collusion! — Donald J. Trump (@realDonaldTrump) February 16, 2018

“Russia started their anti-U.S. campaign in 2014, long before I announced that I would run for President,” he said. “The results of the election were not impacted.”

Clinton beat Trump in Colorado in 2016.

The Associated Press contributed to this report.