United States officials have announced the first charges resulting from an investigation of Russian efforts to influence the U.S. presidential election last year.

A federal grand jury indicted Paul Manafort and Rick Gates on Monday. Manafort served briefly as chairman of Donald Trump's election campaign. Gates is his business partner, who also worked for the Trump campaign.

The two men were charged with 12 criminal counts. These include conspiring against the United States, acting as unregistered foreign agents, and other charges related to hiding tens of millions of dollars overseas.

Both Manafort and Gates pled not guilty in federal court.

These are the first charges Special Counsel Robert Mueller has made public in his five-month investigation, but the indictments did not relate directly to the U.S. election.

Officials say Manafort and Gates worked for years as political advisers and lobbyists. They were charged in connection with their work for the government of Ukraine, two Ukrainian political parties, and former president Viktor Yanukovych.

The indictments came on same day that Mueller announced that a former Trump campaign aide pled guilty earlier this month to lying to federal agents.

In court papers, George Papadopoulos admitted lying about his contacts with "foreign nationals" who he thought had close ties to Russian officials. Papadopoulos once served as a foreign policy adviser to the Trump campaign. He is said to be cooperating with investigators.

Court papers show that Papadopoulos was told about the Russians possessing "dirt" on Hillary Clinton in the form of "thousands of emails" on April 26, 2016. This was before it became public that the Democratic National Committee and John Podesta's emails had been hacked. Podesta served as chairman of Clinton's presidential election campaign.

At the White House, presidential spokesperson Sarah Huckabee Sanders said Mueller's announcement had nothing to do with the Trump campaign. Papadopoulos, she noted, was a volunteer.

"It has nothing to do with the activities of the campaign. It has to do with his failure to tell the truth. That doesn't have anything to do with the campaign or the campaign's activities."

She added that the investigation should look into Clinton's election campaign.

Earlier on Monday, President Trump also said investigators should be looking at his former opponent. And he tweeted that the Manafort indictment was related to events that took place before the 2016 campaign.

"Sorry, but this is years ago, before Paul Manafort was part of the Trump campaign. But why aren't Crooked Hillary & the Dems the focus?????," he tweeted.

The president added, "Also, there is NO COLLUSION!"

Collusion between the Trump campaign and Russia is what Mueller has been investigating since he was named Special Counsel last May.

Manafort joined Trump's election campaign in March 2016. Trump pushed him out in August because of reports about Manafort's foreign consulting work.

The indictment accuses Manafort and Gates of nearly 10 years of secretly plotting to work for Ukrainian interests. It says more than $75 million passed through financial accounts outside the United States, and that Manafort hid more than $18 million.

Manafort and Gates worked for pro-Russian groups in Ukraine between 2006 and 2015. That investigation is now also part of Mueller's larger investigation.

I'm Anne Ball.

Anne Ball wrote this story for VOA Learning English. The editor was George Grow.