Reacting on "Fox & Friends" to news that Hunter Biden's tax affairs are the subject of a federal investigation on Thursday, Fox News contributor Sarah Sanders said Thursday that liberal media outlets "covered it up" for him during his father's presidential campaign.

"It's not surprising, but it's frankly very disturbing," she said. "President Trump spent days and weeks and months talking about trying to get the liberal media to cover this, and it's not shocking that they absolutely, not just refused to cover it, but frankly I think covered it up in many cases and refused to hold the fire on Biden and certainly on these business dealings."

The investigation by the U.S. Attorney's Office in Delaware has been ongoing since 2018, and sources tell Fox News it was predicated, in part, by Suspicious Activity Reports (SARs) regarding suspicious foreign transactions, including with China. Biden's past business dealings with Chinese nationals linked to the Communist government and the People's Liberation Army are also outlined in a Senate Homeland Security Committee report, although it is unclear if those dealings are part of the Delaware office's probe.

HUNTER BIDEN'S CHINA BUSINESS DEALS LEADING UP TO 2018 PROBE DETAILED IN SENATE REPORT

It's also unclear if the investigation is tied to the federal subpoenas for a laptop purportedly belonging to Biden in late 2019. Big Tech companies Facebook and Twitter came under fire in October for suppressing a New York Post story that published emails from the laptop, and some media outlets promoted the idea that it was a Russian smear campaign.

Sanders slammed the two industries for what she described as a collaborative effort to boost Biden and his father, President-elect Joe Biden.

"Look, at the end of the day, China is one of our biggest national security threats and also our greatest economic competitor," Sanders said. "This is absolutely, I think, very disturbing and very alarming to see this type of relationship between Hunter Biden and our greatest competitor, our greatest national security threat. That is something that everyone should be paying attention to and another reason that it is so important to make sure that what took place in this election between Big Tech and the liberal media, refusing to cover key and important issues and favor one candidate over another, absolutely can never happen again."

MEDIA FINALLY COVERS HUNTER BIDEN STORY AFTER AVOIDING CONTROVERSY BEFORE ELECTION

Sanders, who served as White House press secretary from 2017 to 2019, said if she had even "eaten at a Chinese restaurant," the press would have made hay about it.

She also reacted to Rep. Eric Swalwell's, D-Calif., claim that a recent report about a Chinese spy who gained access to him was leaked because of his criticism of the Trump administration.

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"He was too busy, actually, getting things done than to focus on Eric Swalwell, but I do commend [House Minority Leader] Kevin McCarthy for calling this out, questioning whether or not he should be on [the Intelligence] committee," Sanders said.

Fox News' Brooke Singman contributed to this report.