The U.S. has accused a suspected Chinese intelligence operative of sleeping with at least two American mayors, The Telegraph reported Wednesday.

The intelligence officer developed relationships with a number of American officials as part of a yearslong spying campaign aimed at influencing U.S. politicians early in their careers.

News website Axios released information of what it said was a yearlong probe into the activities of a Chinese woman called Fang Fang or Christine Fang.

Axios said that Fang became close to a number of politicians in the San Francisco Bay area between 2011 and 2015. Rep. Tulsi Gabbard and Rep. Eric Swalwell both ran for president in the Democratic presidential primary this year, the news outlet said.

There is no evidence in the records of the Federal Election Commission that Fang herself bankrolled Swalwell's electoral campaign. Funding from foreign entities is illegal.

Swalwell refused to participate in the Axios story in order to "protect information that might be classified," the National Review reported.

Swalwell hasn't been accused of any misdeeds and said he severed relations with Fang as soon as he found out about her alleged ties to China, Axios reported. Gabbard said through a representative that she didn't remember "ever meeting or talking with" Fang.

Reports said she was involved in sexual relationships with at least two mayors from a Midwestern city over a three-year period. Fang, who was in her late 20s at the time, was studying at the California State University in East Bay. According to a U.S. official, an FBI surveillance caught a sexual encounter involving Fang and a mayor from Ohio.

By middle of 2015, Fang abruptly left the U.S. and returned to China. Her sudden departure was a surprise to many of her Bay Area political friends. She hasn't returned to the U.S.