WASHINGTON (CN) – The Senate Judiciary Committee has opened a probe into former Attorney General Loretta Lynch for her possible role in thwarting the FBI from investigating Hillary Clinton during the 2016 presidential campaign.

Committee Chairman Sen. Chuck Grassley, R.-Iowa, joined by Sen. Dianne Feinstein, D.-Calif., Sen. Lindsey Graham, R.-S.C., and Sen. Sheldon Whitehouse, D.-Rhode Island, submitted a letter to Lynch on Thursday.

Specifically, the committee wants to know more about an email or memo written by a Democratic operative who expressed confidence that Lynch would keep the Clinton investigation from going “too far,” the committee said in a press release on Friday.

“According to anonymous government officials cited [in a 2016 FBI report,] the discovery of the document ‘complicated’ how FBI and the Justice Department would interact in the investigation because ‘if Ms. Lynch announced the case was closed, and Russia leaked the document, Mr. Comey believed it would raise doubts about the independence of the investigation,” the three-page letter stated.

Former FBI director James Comey raised the same concern publicly during a Senate Oversight Committee hearing on May 3, just a week before President Donald Trump unceremoniously removed him from his post.

At that hearing, Comey told the senators that his concern over possible ethical impropriety involved in the Clinton investigation gave him pause.

“The normal way to do it would be to have the Department of Justice announce it, and I struggled, as we got closer to the end of it, with — a number things had gone on, some of which I cannot talk about yet, that made me worry that the Department leadership could not credibly complete the investigation and decline prosecution without grievous damage to the American people’s confidence in the justice system,” Comey said. “And then the capper was — and I am not picking on the Attorney General, Loretta Lynch, who I like very much. But her meeting with President Clinton on that airplane was the capper for me. And I then said, you know what? The Department cannot by itself credibly end this.”

This scenario is one Comey often relied on to explain why he broke with the usual practice of the Justice Department in order to reveal his findings.

The committee also asked Lynch to clear up confusion surrounding a news report in late May which indicated that Russian intelligence obtained a document that “referred to an email supposedly written by the then-chair of the Democratic National Committee Rep. Debbie Wasserman Schultz, and sent to Leonard Bendardo, an official with the Open Society Foundations,” the letter said.

In that email, the committee said that Wasserman Schultz admitted Lynch had private talks with a senior Clinton campaign staffer, Amanda Renteria. The email is said to contain details confirming that Lynch told Renteria she would make sure the FBI’s investigation into Clinton failed to run its course.

The committee posed several other questions to Lynch in the letter: Did anyone from the FBI ever discuss or mention these emails? If she is aware of any document, how and when did she become aware of their existence? Does she have any reason to doubt their authenticity? Has she ever actually communicated with Renteria and if so, when? Did the Justice Department ever have communication with Wasserman Schultz, her staff, associates or any other current or former DNC officials regarding the Clinton email investigation?

While it awaits Lynch’s response, the committee is pressing forward with its investigation of Trump’s May 9 firing of Comey.

During an interview on the “Fox and Friends” television show Friday morning, Trump called the investigation into allegations of Russian collusion “ridiculous” and proceeded to question the nature of Comey’s supposed friendship with special counsel Robert Mueller.

Noting that Mueller and Comey were “very, very good friends,” Trump also called Mueller “honorable” and a man who will “hopefully come up with an honorable conclusion.”

Trump also speculated on the roster of attorneys Mueller has wrangled together for the investigation.

“I can say that the people that have been hired are all Hillary Clinton supporters, some of them worked for Hillary Clinton. I mean the whole thing is ridiculous if you want to know the truth,” Trump said.