Updated

Rep. Eric Swalwell, D-Calif., is keeping quiet about his past relationship with a woman suspected of acting as a Chinese spy.

Axios reported that a Chinese national named Fang Fang or Christine Fang targeted up-and-coming local politicians, including Swalwell. Fang reportedly helped fundraise for Swalwell's 2014 campaign and helped place at least one intern in his office.

In fact, a former intelligence official told Fox News the Chinese for years have sent spies to “sleep with lesser-known members of Congress and staffers.”

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Fang's relationships with at least two Midwestern mayors turned sexual, according to Axios, with at least two incidents being caught by FBI surveillance. When asked about the nature of Swalwell's relationship with Fang, the Democratic congressman's office declined to comment.

According to Axios, federal investigators gave Swalwell a defensive briefing in 2015 during which they alerted him to their concerns over Fang. An intelligence official told the news outlet that Swalwell cut ties with her soon after.

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The congressman's office told Axios that  Swalwell "long ago, provided information about this person — whom he met more than eight years ago, and whom he hasn’t seen in nearly six years — to the FBI." Beyond that, however, his office would not discuss the story, citing concerns related to classified information.

An anonymous FBI official told the San Francisco Chronicle that "Swalwell was completely cooperative and under no suspicion of wrongdoing."

"It was a defensive briefing," the official told the Chronicle. "Information was obtained where we do a duty to warn ... that he may be targeted by a foreign government."

Fang also volunteered for the 2014 House bid of Rep. Ro Khanna, D-Calif., and a 2013 fundraiser for Rep. Tulsi Gabbard, D-Hawaii. Khanna’s office said the congressman saw Fang at several gatherings but had no further contact, while Gabbard’s office told the outlet she "has no recollection of ever meeting or talking with [Fang], nor any recollection of her playing a major role at the fundraiser.”

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Fang reportedly left the U.S. in mid-2015.

Fox News' Adam Shaw contributed to this report.