Prosecutors pursuing sexual assault charges against Bryon Hefner say they also want records on “additional’’ potential victims who spoke to attorneys hired by the state Senate to investigate his husband, former Senate president Stanley C. Rosenberg — a sign they could seek to expand the case against the 31-year-old.

Attorney General Maura T. Healey’s office filed a motion on Wednesday in Suffolk Superior Court seeking a court order to obtain interviews conducted by the firm Hogan Lovells US LLP as it compiled a blistering report on Rosenberg.

Prosecutors, who cited four victims when a grand jury indicted Hefner in March, said the firm interviewed many of the same people they did. But they said the Senate report also contains information on “additional persons who alleged that they were sexually assaulted or harassed by the defendant.’’

“Statements of additional persons, not now alleged victims in this matter, contain evidence relevant to the defendant’s state of mind, modus operandi, pattern, scheme or plan,’’ Jennifer L. Snook, an assistant attorney general, wrote in the three-page motion.

“Statements of existing witnesses may corroborate what they told state and Boston police [or] the grand jury,’’ Snook added, “but may also contradict their prior statements or otherwise provide information favorable to the defendant and thus be exculpatory.’’

Prosecutors allege Hefner engaged in a pattern of assault and misconduct over multiple years. They detailed the alleged acts in vivid terms — saying Hefner groped two men against their will, kissed another “aggressively on the lips without his consent,’’ and boastfully showed nude photos of a fourth man who said he had never agreed to have the pictures taken.

But the Senate investigation into Rosenberg expanded the universe of people who say Hefner sexually assaulted them.

Two of the accounts in the Senate report were not included in either the initial criminal charges brought against Hefner or a November story published by the Globe, in which four men said Hefner had sexually assaulted and harassed them and bragged he could influence Senate business.

Snook said prosecutors need a judge’s approval to gain access to the records because they cannot reasonably obtain them “absent an order from this court.’’ Citing the desire of victims and witnesses to maintain privacy, prosecutors also said they would not make the documents public before trial.

The Senate wrote in its report that it would keep confidential the identity of any victim or witness unless the person consented to being identified, or if “disclosure is required by judicial process or procedure,’’ Snook wrote in the motion.

“The materials sought will likely include recitations of sexual assaults or other misconduct alleged to have been committed by the defendant,’’ Snook wrote.

The order prompted senators to reassert their commitment to keeping witnesses in its investigation confidential, though Senator Michael J. Rodrigues, who chairs the chamber’s Committee on Ethics, said the chamber would not violate a court order.

“The Senate is very firm in its insistence that we do everything possible that we can to maintain the [witnesses’] confidentiality,’’ the Westport Democrat said.

Aides to Senate President Harriette Chandler said her office is reviewing its options.

“Our review will be predicated on maintaining the promise made to witnesses that we will preserve their confidentiality to the fullest extent possible,’’ Chandler said in a statement. “The Senate investigation was built on an ideal of privacy for those witnesses who came forward. We continue to stand by that ideal.’’

Efforts to reach Anthony E. Fuller, an attorney at Hogan Lovells who helped lead the Senate probe, were not successful Wednesday.

Healey’s office filed the motion as part of a brief hearing in Suffolk Superior Court, in which attorneys agreed to return to court on July 24.

Hefner didn’t appear at the courthouse Wednesday. He is staying at an out-of-state treatment facility, according to court filings. His attorney, Tracy A. Miner, declined to comment further on the program Hefner is attending.

Hefner pleaded not guilty in April to five counts of sexual assault, four counts of distributing nude images without consent, and one count of criminal lewdness.

A trial is tentatively scheduled for 2019.

At the time, Miner said in a statement that Hefner “looks forward to defending himself in a court of law where accusers cannot remain anonymous and must face cross-examination. Unfortunately, he has already been pilloried in the press for political purposes, having never had a trial.’’

Rosenberg, who had stepped down from his Senate president’s post in December, resigned from his seat shortly after the Senate released its report.

Hefner could one day also receive tens of thousands of dollars in state retirement benefits after Rosenberg filed an application last week with the State Retirement Board that designates his husband as the beneficiary for his pension in case of his death, the Globe reported.

State statute doesn’t preclude a beneficiary from receiving the pension even if the beneficiary has been convicted criminally.

Reach Matt Stout at matt.stout@globe.com. Follow him on Twitter @mattpstout.