Terry McAuliffe, Virginia's Democratic governor and chairman of Hillary Clinton's 2008 presidential run, is under federal investigation over contributions to his 2013 campaign, CNN said on Monday, citing unnamed U.S. officials.

The U.S. Justice Department's year-long investigation has focused, at least in part, on whether contributions to Mr. McAuliffe's gubernatorial campaign, including $120,000 from a Chinese businessman, Wang Wenliang, violated the law, according to CNN.

Investigators have "scrutinized" McAuliffe's time as a board member of the Clinton Global Initiative, part of the charitable foundation set up by former President Bill Clinton, CNN said, citing unidentified government officials briefed on the case.

The foundation is not accused of any wrongdoing, CNN added.

McAuliffe spent at least 15 years as an unpaid director for the foundation, now known as the Bill, Hillary & Chelsea Clinton Foundation, until 2013, according to the charity's annual disclosures filed with the Internal Revenue Service.

An attorney for McAuliffe's campaign, Marc Elias, said he could not confirm the CNN report.

"Neither the governor nor his former campaign have knowledge of this matter, but as reported, contributions to the campaign from Mr. Wang were completely lawful," Elias said in a statement. "The governor will certainly cooperate with the government if he is contacted about it."

The Justice Department declined to comment.

Spokesmen for Clinton and the Clinton Foundation did not immediately respond to requests for comment. A spokeswoman for Mr. Wang, who has given at least $2 million to the Clinton Foundation through his company Rilin Enterprises, said he had not been contacted by investigators.

McAuliffe is a close ally of Hillary Clinton, the front-runner for the 2016 Democratic presidential nomination. He was co-chairman of Bill Clinton's 1996 presidential re-election campaign and chaired Hillary Clinton's 2008 presidential bid.

On Sunday, McAuliffe hosted a fundraiser for Mr. Clinton's campaign. For a $2,700 donation, a person attending the event could get a photo taken with him, according to Clinton's website.

Republicans seized on the report to question Clinton's integrity. Her aides have been questioned by the FBI and Justice Department prosecutors in a probe into whether her using a private email server as secretary of state broke laws.

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"Hillary Clinton's campaign was already tainted by her own FBI investigation, so the revelation that her top political ally Terry McAuliffe is also facing a criminal probe is especially damaging," Michael Short, a Republican National Committee spokesman, said in a statement.

(Reporting by Eric Beech and Timothy Ahmann in Washington and Jonathan Allen in New York; Editing by Eric Walsh and Peter Cooney)