Former FBI Director James Comey started to draft a statement exonerating Hillary Clinton in the bureau's investigation into her use of a private email server before the FBI interviewed her or her key witnesses, the Senate Judiciary Committee said Thursday.

"Conclusion first, fact-gathering second — that's no way to run an investigation. The FBI should be held to a higher standard than that, especially in a matter of such great public interest and controversy," Senate Judiciary Committee Chairman Chuck Grassley, R-Iowa, and Judiciary Subcommittee Chairman Lindsey Graham, R-S.C., said in a letter to the FBI.

The Judiciary Committee reviewed transcripts, which were heavily redacted, indicating Comey began drafting the exoneration statement in April or May 2016, before the FBI interviewed up to 17 key witnesses, including Clinton and some of her close aides.

Comey's work on the statement also came before the Justice Department entered into immunity agreements with Cheryl Mills, Clinton's chief of staff while she was Secretary of State, and Heather Samuelson, who served as the State Department's White House liaison.

Comey announced in July 2016 the FBI wouldn't recommend criminal charges against Clinton.

Democrats in Congress alleged last fall that Comey's actions in the FBI's investigation into Clinton's email use violated the Hatch Act, which caused the Office of Special Counsel to launch an investigation.

During its investigation, the Office of Special Counsel interviewed James Rybicki, Comey's chief of staff, and Trisha Anderson, the principal deputy general counsel of national security and cyberlaw, who were close to Comey at the FBI.

The Office of Special Counsel shared those interview transcripts at Grassley's urging after Comey was fired.

In their interview with Anderson, the Office of Special Counsel asked when she first learned Comey was planning to make a public statement about the Clinton investigation.

"I'm not entirely sure exactly when the idea of the public statement first emerged," Anderson said. "It was, I can't, I can't put a precise timeframe on it, but [redacted] ... And then I believe it was in early May of 2016 that the director himself wrote a draft of that statement."

In his interview, Rybicki told the Office of Special Counsel that Comey emailed several people in the spring "to say, you know, again knowing sort of where—knowing the direction the investigation is headed, right, what would be the most forward-leaning thing we could do."

When asked whether the Comey statement was drafted in either April or early May, before Clinton herself was interviewed by the FBI, Rybicki said that was correct.

In their letter to the FBI, Grassley and Graham requested drafts of Comey's statement closing the Clinton email investigation, including his initial draft from April or May and his final statement. The senators also asked for all records related to communications from FBI officials related to Comey's draft statement, and records provided to the Office of Special Counsel.