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© Drew Angerer/Getty ImagesFormer Secretary of State Hillary Clinton delivers the commencement address at the Hunter College Commencement ceremony at Madison Square Garden, May 29, 2019 in New York City.
A special federal prosecutor in Utah is close to completing an investigation into former Secretary of State Hillary Clinton, according to Attorney General William Barr.

Barr told CBS News in an interview published on May 31 that U.S. Attorney John Huber investigation of Clinton is "winding down."

Then-Attorney General Jeff Sessions announced in a letter (pdf) on March 29, 2018, that he had assigned Huber to investigate a list of potential crimes outlined by Republicans in Congress.

"The other issues he's been working on relating to Hillary Clinton. Those are winding down and hopefully we'll be in a position to bring those to fruition," Barr said.

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© Aaron P. Bernstein/ReutersAttorney General William Barr returns to a Senate Judiciary Committee hearing entitled "The Justice Department's Investigation of Russian Interference with the 2016 Presidential Election." on Capitol Hill on May 1, 2019.
While Barr did not specify the "issues" Huber is investigating, Sessions announced Huber's assignment last year in response to "recent letters" from three Republicans in Congress: Sen. Chuck Grassley, Rep. Bob Goodlatte, and Rep. Trey Gowdy.

Gowdy and Goodlatte penned one such letter (pdf) on March 6, 2018, calling on Sessions to appoint a second special counsel "to review decisions made and not made by the Department of Justice and the FBI in 2016 and 2017."

The lawmakers wrote that the second special counsel should review evidence of bias by federal government employees, how decisions to charge or not charge people with crimes were made, and whether the surveillance of the Trump campaign was "appropriate and devoid of extraneous influence."

Based on the content of that letter, Huber may be investigating one or more of the Clinton-related matters the FBI was pursuing in 2016 and 2017.
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© Courtesy Justice DepartmentAttorney General William Barr shakes hands with U.S. Attorney John Huber at the Justice Department in Washington, D.C., in March, 2019.
From 2015 to 2016, the bureau investigated whether Clinton and her associates mishandled classified information by using an unauthorized private email server to conduct official government business during her time as the secretary of state. During the same time frame, the bureau was investigating allegations concerning the Clinton Foundation, according to the Wall Street Journal.

Huber may also be investigating whether the approval of the sale of Canadian mining company Uranium One to Russia had any connection to millions of dollars that parties who benefited from the deal gave to the Clinton Foundation. Republicans have called on Sessions to investigate the matter since as early as 2017. Sessions told the House Judiciary Committee in November 2017 that he had assigned federal prosecutors to investigate the matters.

Notably, Uranium One had significant holdings in Utah, where Huber is based, including a small town, a uranium mill, and more than 10,000 acres of uranium claims.

Clinton lost the 2016 presidential election to Trump. Since taking office, Trump has urged the Justice Department to investigate Clinton.

"Uranium deal to Russia, with Clinton help and Obama Administration knowledge, is the biggest story that Fake Media doesn't want to follow!" Trump wrote on Twitter in October 2017.

The sale of Uranium One became a major story in the run-up to the 2016 election. The bulk of the issues with the sale was exposed in Clinton Cash, a book by Peter Schweizer which detailed how millions of dollars flowed to the Clinton Foundation while Clinton's State Department was approving the Uranium One sale.