U.S. senators Patty Murray and Maria Cantwell, D-Wash., are calling for an investigation into whether Attorney General Jeff Sessions violated his promise to recuse himself from the investigation into Russia's alleged interference with the 2016 presidential election.

Murry and Cantwell joined nine other Democratic senators Wednesday in calling for Inspector General Michael Horowitz to investigate after Sessions wrote a letter to President Donald Trump recommending the firing of FBI Director James Comey on May 9. Deputy Attorney General Rod Rosenstein also wrote a letter to Trump critical of Comey, citing Comey's handling of the investigation into Hillary Clinton's emails.

Comey was leading the Russia investigation at the time he was fired.

“It is clear that Attorney General Sessions had an active role in the termination of Director Comey," the senators said in a letter. "This seems to be in direct violation of Attorney General Sessions’ recusal from ‘any existing or future investigations of any matter relating in any way to the campaigns for president of the United States.’"

Trump told NBC News he had already made up his mind about firing Comey before receiving the letter.

Read the full letter below.

Dear Mr. Horowitz:

Shortly after Attorney General Jeff Sessions was confirmed by the U.S. Senate, the Washington Post published a story on March 1, 2017, entitled “Sessions Met with Russian Envoy Twice Last Year, Encounters He Later Did Not Disclose.” One day later on March 2, 2017, Attorney General Sessions held a news conference announcing he would recuse himself from all matters related to investigations connected to the 2016 presidential campaign.

The recusal of a senior member of the Department of Justice related to a high profile investigation is always a significant act. However, as Attorney General Sessions himself stated at the news conference announcing his recusal “[i]f a specific matter arose where I believed my impartiality might reasonably be questioned.” This recusal is required by with the Department of Justice regulations relating to conflicts of interest, 28 CFR § 45.2:

…[N]o [D.O.J.] employee shall participate in a criminal investigation or prosecution if he has a personal or political relationship with: (1) Any person or organization substantially involved in the conduct that is the subject of the investigation or prosecution; or (2) Any person or organization which he knows has a specific and substantial interest that would be directly affected by the outcome of the investigation or prosecution. 28 CFR § 45.2(a)(1) & (2).

A “political relationship” is defined as “…a close identification with an elected official, a candidate (whether or not successful) for elective, public office, a political party, or a campaign organization, arising from service as a principal advisor thereto or a principal official there of...” 28 CFR § 45.2(c)(1). A “personal relationship” is defined as “a close and substantial connection of the type normally viewed as likely to induce partiality...” 28 CFR § 45.2(c)(2).

Attorney General Sessions acted as a surrogate for then candidate Trump’s campaign for president on numerous occasions including appearing and speaking at campaign events in support of candidate Trump. Further, reports that the Attorney General met with representatives of the Russian government, regardless of the capacity, lend credence to the specter of partiality that would arise over Attorney General Sessions’ oversight or participation in any investigation that touches upon the 2016 Presidential campaign, or the investigation of Russian involvement and attempts to influence the outcome of the subsequent election.

The Attorney General recused himself from any involvement in the investigations surrounding the 2016 Presidential campaign. The Attorney General’s recusal language itself could not be clearer “I have now decided to recuse myself from any existing or future investigations of any matter relating in any way to the campaigns for president of the United States.” Attorney General Sessions Statement on Recusal, March 2, 2017.

Despite this recusal, Attorney General Sessions appears to have been intimately involved with the May 9, 2017 dismissal of Federal Bureau of Investigation (“F.B.I.”) Director James Comey, who was in charge of an investigation of the Trump campaign and its ties to Russia. On Monday, May 8, 2017, Attorney General Sessions went to the White House for a meeting with President Trump and Rod Rosenstein, his Deputy Attorney General, in order to discuss the removal of Director Comey.

On May 9, 2017, Attorney General Jeff Sessions sent a letter to President Trump recommending the termination of Director of the F.B.I. James B. Comey, Jr. Attorney General Sessions stated “I have concluded that a fresh start is needed at the leadership of the F.B.I…Therefore, I must recommend that you remove Director James B. Comey, Jr.”

In his termination letter to Director Comey, President Trump stated that he had received a letter “from the Attorney General [Sessions]…recommending your dismissal” as Director of the F.B.I. The following day, Attorney General Sessions reportedly began interviewing candidates to serve as the interim replacement for Director Comey – candidates who would temporarily lead the F.B.I.’s ongoing investigation into the Trump campaign.

It is clear that Attorney General Sessions had an active role in the termination of Director Comey. This seems to be in direct violation of Attorney General Sessions’ recusal from “any existing or future investigations of any matter relating in any way to the campaigns for president of the United States.” At the time of his termination, Director Comey was actively leading the F.B.I.’s investigations into both the attempts by the Russian government to influence the 2016 presidential campaign, and the ties of members/employees/representatives of the Trump Campaign had, or have, with the Russian government or Russian intelligence services.

It is imperative that the American people have faith in the institutions that are investigating the influence a hostile foreign power may have had on our presidential campaign, election, and the current administration of President Trump. We believe the Attorney General’s involvement in the termination of Director Comey has injected the exact “partiality” in these investigations he claimed to wish to avoid. Further, the President’s recent admission that Comey was fired, at least in part, due to the Russia investigation only raises further questions about the role of the Attorney General in the termination, his willingness to provide cover for a political decision, and both his and the Department of Justice’s ability to perform an independent investigation. His involvement seems to be a clear violation of his recusal, and can only be construed as an attempt to influence an ongoing investigation that threatens to examine his own role in the 2016 presidential campaign, as well other elements of President Trump’s campaign and administration.

We urge you to investigate whether Attorney General Sessions has violated his recusal, and the rules and regulations that govern it. Further, we ask that if you find a violation that you explore what effect such a violation may have on the ongoing investigations, and how the integrity of these investigations can be restored. In addition to any related matter you find appropriate, we ask that you specifically seek to answer the following questions:

1. To what extent is Attorney General Sessions required to recuse himself from investigations into matters related to the Trump campaign under 28 C.F.R. § 45.2, or any other relevant rules and regulations?

2. What was the scope of Attorney General Sessions’ publicly announced March 2, 2017 recusal?

3. What is the timeline of Attorney General Sessions’ involvement in the removal of F.B.I. Director James Comey? Did his involvement in Director Comey’s termination violate his recusal agreement or requirements, or other DOJ rules, regulations, and precedents?