Supreme Court Marshal Gail Curley made the statement a day after the court released a 20-page report based on the investigation that failed to identify who leaked the draft to the news organization Politico. The court on Thursday had not made clear whether the nine justices who served on the court at the time of the leak had been interviewed during the inquiry.

"During the course of the investigation, I spoke with each of the justices, several on multiple occasions," Curley said in the statement, released by the court. "The justices actively cooperated in this iterative process, asking questions and answering mine."

The report said investigators interviewed 97 court employees.

"I followed up on all credible leads, none of which implicated the justices or their spouses," Curley said.

She said on that basis, she decided it was not necessary to asks the justices to sign sworn affidavits affirming they did not leak the draft opinion, something court employees by contrast were required to do.

(Reporting by Nate Raymond in Boston; Editing by Will Dunham)

By Nate Raymond