The top Democrat on the Senate Judiciary Committee, Dianne Feinstein of California, said Thursday that she has referred a letter concerning Supreme Court nominee Brett Kavanaugh to federal authorities.
"I have received information from an individual concerning the nomination of Brett Kavanaugh to the Supreme Court," Feinstein said. "That individual strongly requested confidentiality, declined to come forward or press the matter further, and I have honored that decision. I have, however, referred the matter to federal investigative authorities."
Feinstein's announcement came shortly after the committee set a date to vote on Kavanaugh's nomination over the objections of Democrats.
Later Thursday, The Washington Post, citing a person familiar with the matter, reported that the FBI did not plan to open an investigation. The law enforcement agency included the letter as an update to Kavanaugh's background check provided to the White House, a spokesperson for the bureau told CNBC.
Feinstein's disclosure came during the last weeks of Kavanaugh's confirmation process, and followed a report Wednesday night in the investigative news outlet The Intercept that first disclosed the existence of the letter. According to the outlet, the letter is rumored to include details about an incident involving Kavanaugh that took place during his time at Georgetown Preparatory School in Maryland.
The incident involved possible sexual misconduct between Kavanaugh and a woman who was also in high school at the time, two officials familiar with the matter told The New York Times. CNBC has not independently confirmed the contents of the letter.
Sen. Dick Durbin, D-Ill., told Buzzfeed News earlier in the day that the letter had been referred to the FBI. A source familiar with the matter confirmed Durbin's comments to CNBC Thursday.
The letter was reportedly written by someone affiliated with Stanford University. It was sent to Rep. Anna Eshoo, who represents California's 14th District, before being passed along to Feinstein.
A spokesperson for Eshoo's office declined to comment on the matter.
"Our office has a confidentiality policy regarding constituent casework," the spokesperson told NBC News.
Feinstein has not shared details about the letter beyond her statement Thursday, and no other senators on the Judiciary Committee have been permitted to see it, according to reports.
The woman who is the subject of the letter is reportedly represented by Debra Katz, a whistleblower attorney who has been described as "Washington's top attorney for women who want to fight back" in a profile in the magazine The Washingtonian.
Katz, who did not respond to a request for comment from CNBC, represented one of the women who accused former New York Attorney General Eric Schneiderman of physical abuse before he was forced to resign earlier this year.
She has not confirmed that she is the attorney for the woman who is the subject of the letter.
"There's nothing to say," Katz told BuzzFeed News Wednesday. The website reported that Katz was on Capitol Hill Wednesday following the publication of The Intercept report. She was leaving as Judiciary Committee Democrats were meeting in the lobby of the Senate.
A spokesperson for Judiciary Committee Chairman Chuck Grassley, R-Iowa, told CNBC on Thursday that he was aware of the referral but suggested that it would not cause any delays in the confirmation process.
"There's no plan to change the committee's consideration of Judge Kavanaugh's nomination," the spokesperson said.
The committee is scheduled to vote on Kavanaugh's nomination Sept. 20, and a full vote from the Senate is expected as soon as late September. Republicans hope to have Kavanaugh confirmed ahead of the start of the Supreme Court term in October.
In a statement, White House spokesperson Kerri Kupec said that the FBI "has thoroughly and repeatedly vetted Judge Kavanaugh, dating back to 1993, for some of the most highly sensitive roles."
"Not until the eve of his confirmation has Sen. Feinstein or anyone raised the specter of new 'information' about him," Kupec said. "Senator Schumer promised to 'oppose Judge Kavanaugh's nomination with everything I have,' and it appears he is delivering with this 11th hour attempt to delay his confirmation."
A spokesperson for Senate Minority Leader Chuck Schumer of New York said that Schumer has not had access to the letter but believes that the Judiciary Committee is handling it appropriately.
Sen. John Cornyn of Texas, the second ranking Republican on the Judiciary Committee, expressed skepticism.
"Let me get this straight: this is statement about secret letter regarding a secret matter and an unidentified person," Cornyn wrote in a post on Twitter. "Right."