The FBI investigation into allegations of sexual assault against Brett Kavanaugh is concentrating on what happened at a teenage party in the Maryland suburbs on July 1, 1982.

Christine Blasey Ford, Kavanaugh's main accuser, said she could not remember exactly when or where the alleged assault happened but an entry on the future judge's calendar placed several key people at a party on July 1 of the summer in question.

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The entry stated: “Go to Timmy’s for skis w/ Judge, Tom, PJ, Bernie, Squi.” In his Senate testimony, Kavanaugh identified those friends as Tim Gaudette, Mark Judge, Tom Kane, P.J. Smyth, Bernie McCarthy, and Chris Garrett - whose nickname was “Squi” and who briefly dated Ford. The judge added that “skis” meant “brewskis," for beer.

In her Senate testimony, Ford, a California psychology professor, said that when she was 15 years old, Kavanaugh, then 17 years old, pinned her to a bed and groped her while he and Judge, who she claimed was in the room at the time, laughed at her.

She said her friend Leland Keyser was also there, adding: "There were four boys I remember specifically being there: Brett Kavanaugh, Mark Judge, a boy named P.J. and one other boy whose name I cannot recall."

Gaudette, Judge, Garrett and Keyser have all been interviewed by the FBI while Kane told CNN he would "rather not say" if investigators had quizzed him. McCarthy has not responded to media requests for comment.

[Also read: When will the FBI interview Christine Blasey Ford?]

William Sullivan, a lawyer for Chris Garrett, said Garrett had been questioned by the FBI. “Mr. Garrett has voluntarily cooperated with the FBI inquiry, and has completed his interview,” he told the Washington Examiner in an email.

Ken Eichner, who represents Gaudette, told CNN Wednesday: "I can confirm that Mr. Gaudette interviewed with special agents today, however, we are going to respectfully decline to elaborate on the interview."

Democrats have honed in on the July 1 party, suggesting it could hold the key to verifying Ford's unsubstantiated claims.

But Kane previously cast doubt on whether Ford, who identified the house as a single family home near Columbia Country Club, could have been referring to a party at Gaudette's. He told CNN. “Tim Gaudette lived in Rockville. It’s 11 miles away from Columbia Country Club. And it wasn’t a single-family home. It was a townhouse.”

Smyth, his lawyer said in a statement, had "truthfully answered every question the FBI asked him and, consistent with the information he previously provided to the Senate Judiciary Committee, he indicated that he has no knowledge of the small party or gathering described by Dr. Christine Blasey Ford nor does he have any knowledge of the allegations of improper conduct she has leveled against Brett Kavanaugh."

Keyser's lawyer Howard Walsh submitted a statement to the Senate Judiciary Committee denying any knowledge: “Simply put, Ms. Keyser does not know Mr. Kavanaugh and she has no recollection of ever being at a party or gathering where he was present, with, or without, Dr Ford."

Kavanaugh has categorically denied the allegation and said he was never at the party described by Ford.

With its interviews with the attendees of the party, the FBI has expanded its list of interviewees beyond the initial four the White House directed the bureau to interview.

Those four were Deborah Ramirez, who accused Kavanaugh of exposing himself during a party at Yale University, Judge, Smyth and Keyser.

John Clune, an attorney for Ramirez, said on Twitter she spoke with the FBI for more than two hours and described the interview as “detailed and productive". Clune said Ramirez gave the FBI a list of more than 20 witnesses who “may have corroborating information” about the alleged incident.

The FBI has until Friday to complete its investigation but could finish as early as Wednesday. Senate Democrats have been urging the bureau to speak to more people who may be able to corroborate both Ford’s and Ramirez’s claims.

In a letter to FBI Director Chris Wray and White House counsel Don McGahn, the Democrats said Kavanaugh and Ford’s husband should also be among those who speak with the FBI. Trump said during a press conference Monday that the FBI should “interview anybody they want, but within reason.”