By NICHOLAS FANDOS and CATIE EDMONDSON, New York Times–

The senior Democrat on the Senate Judiciary Committee referred information involving Judge Brett M. Kavanaugh, President Trump’s nominee to the Supreme Court, to federal investigators on Thursday, but the senator declined to make public what the matter involved.

Two officials familiar with the matter say the incident involved possible sexual misconduct between Judge Kavanaugh and a woman when they were both in high school. They spoke anonymously because they were not authorized to discuss the matter.

The statement by Senator Dianne Feinstein of California came a week before the Judiciary Committee is to vote on his nomination. “I have received information from an individual concerning the nomination of Brett Kavanaugh to the Supreme Court,” Ms. Feinstein said in a statement. “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.”

The information came in July in a letter, which was first sent to the office of Representative Anna Eshoo, Democrat of California, and accuses the judge of sexual misconduct toward the letter’s author, a person familiar with the letter confirmed.

Ms. Feinstein, who received the letter from Ms. Eshoo’s office, informed fellow Democrats on the Judiciary Committee about its existence and its contents on Wednesday evening but did not share the letter itself. Several Democrats advised her to take its claims to the F.B.I., and others pressed for it to become public.

In addition to criminal investigations, the F.B.I. conducts background checks on all major government appointees, including Supreme Court nominees. The F.B.I. said in a statement on Thursday that it had received Ms. Feinstein’s referral and included it in Judge Kavanaugh’s background file. A bureau official also said that no criminal investigation had been opened related to the matter.

Orrin Hatch, Chuck Grassley, Dianne Feinstein sitting at a table in front of a crowd: Senator Charles E. Grassley, the chairman of the Judiciary Committee, said the panel will hold a vote on Judge Brett M. Kavanaugh’s nomination on Sept. 20.© Erin Schaff for The New York Times Senator Charles E. Grassley, the chairman of the Judiciary Committee, said the panel will hold a vote on Judge Brett M. Kavanaugh’s nomination on Sept. 20.

Including the letter in Judge Kavanaugh’s file allows the White House, and potentially other senators, to view its contents. A copy of the letter was included in an updated background file sent on Thursday to the office of Senator Charles E. Grassley, Republican of Iowa and chairman of the Judiciary Committee.

The White House responded almost immediately.

“Throughout his confirmation process, Judge Kavanaugh has had 65 meetings with senators — including with Senator Feinstein — sat through over 30 hours of testimony, addressed over 2,000 questions in a public setting and additional questions in a confidential session. Not until the eve of his confirmation has Senator Feinstein or anyone raised the specter of new ‘information’ about him,” said White House spokeswoman Kerri Kupec. She added, “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.”

Aides to Senator Chuck Schumer of New York, the Democratic leader, said he has not seen the letter, but he believes the committee is handling the matter appropriately.

But Senator John Cornyn of Texas, the No. 2 Republican in the Senate and a member of the committee, was incredulous.

Senator John Cornyn

@JohnCornyn

Let me get this straight: this is statement about secret letter regarding a secret matter and an unidentified person. Right.

Craig Caplan

@CraigCaplan

Replying to @CraigCaplan and 2 others

Feinstein following today’s Judiciary Cmte meeting on Kavanaugh referred information she received on the Supreme Court nominee to “federal investigative authorities.”

Ms. Feinstein had not shared the letter with Mr. Grassley, who said that nonetheless it would not affect his timeline.

“Senator Grassley is aware of Senator Feinstein’s referral,” said George Hartmann, a spokesman for Mr. Grassley. “At this time, he has not seen the letter in question, and is respecting the request for confidentiality. There’s no plan to change the committee’s consideration of Judge Kavanaugh’s nomination.”

Carrie Severino, chief counsel and policy director of the Judicial Crisis Network, the conservative group pressing for Judge Kavanaugh’s confirmation, condemned Ms. Feinstein’s action: “This has all the indicators of an 11th hour character assassination and a desperate attempt to delay and defeat the nomination of Judge Kavanaugh, who has a sterling reputation in his community, his profession, his church and among hundreds of friends, colleagues and co-workers.”

The move by Ms. Feinstein came after the Senate Judiciary Committee, in a series of party-line votes, rejected Democrats’ efforts on Thursday to subpoena documents and testimony into Judge Kavanaugh’s years as a top White House aide under President George W. Bush.

Democrats have accused Mr. Kavanaugh of evading and misleading the committee during last week’s confirmation hearings, and continuing those charges, volleyed a series of requests for more information centering on some of the most contentious issues that surfaced, including his views on executive power and his relationship with a former Republican Senate aide who stole documents from Senate Democrats.

“We have more questions than answers and the only way to address these concerns about Judge Kavanaugh’s credibility before this committee is to hear from those witnesses,” Senator Richard Blumenthal, a Democrat from Connecticut, said.

The Democratic demands included testimony from the Senate aide, Manuel Miranda, who passed Mr. Kavanaugh documents that were illegally copied from Democratic computers. Senate Democrats grilled the judge during the hearings on whether he knew or suspected that materials he received from Mr. Miranda as staff secretary under President Bush had been taken from the files of Senate Democrats without their authorization.

Committee Democrats also sought to subpoena documents related to Mr. Kavanaugh’s knowledge of Bush-era enhanced interrogation and warrantless wiretapping policies. Democrats have accused Mr. Kavanaugh of playing down his role in each program; he has maintained he was not aware of the policies and learned of them only from news reports.

Republicans rejected each of those requests on Thursday, and dismissed the Democrats’ efforts as theatrical bids to appeal to their bases. Mr. Grassley said they will go ahead with a committee vote on Mr. Kavanaugh’s nomination in Senate on Sept. 20.

Senator Ted Cruz, Republican of Texas, dismissed his Democratic colleagues’ arguments that not enough is known about the judge, pointing to his published opinions as a federal appellate judge.

“Everyone agrees that is the most relevant, the most important source for assessing what kind of justice he would be,” he told reporters.

More documents surrounding the judge’s views continue to trickle out. Senator Cory Booker, Democrat of New Jersey, continued releasing committee confidential documents on Thursday. Late Wednesday night, Mr. Kavanaugh submitted a 263-page written response to the over 1,200 follow up questions submitted by committee members after his confirmation hearings.

In his written answers, as in the hearings, Mr. Kavanaugh largely declined to answer questions on the landmark abortion decision Roe v. Wade or on his views on the scope of presidential power, arguing, “It would be improper for me as a sitting judge and a nominee to comment on issues that might come before me.”

He did, however, answer questions submitted by Democrats related to his personal finances and rumored gambling habits.

Mr. Kavanaugh wrote, “I have not had gambling debts or participated in ‘fantasy’ leagues.” In response to questions on whether he plays in regular or periodic poker games, he responded, “like many Americans, I have occasionally played poker or other games with friends and colleagues.”

He also responded to a moment during his confirmation that went viral, in which he declined to shake the hand of Fred Guttenberg, an anti-gun violence activist whose daughter was killed in the Parkland, Fla., school shooting. Mr. Kavanaugh wrote that he did not recognize Mr. Guttenberg and assumed he was a protester, but expressed regret at their interaction.

“Mr. Guttenberg has suffered an incalculable loss. If I had known who he was, I would have shaken his hand, talked to him, and expressed my sympathy,” Mr. Kavanaugh wrote. “And I would have listened to him.”