Sen. Ron Johnson, R-Wis., is demanding the Justice Department turn over the derogatory text messages about President Trump that longtime FBI investigator Peter Strzok sent to FBI lawyer Lisa Page.

In a letter to Deputy Attorney General Rod Rosenstein sent Thursday, Johnson, the chairman of the Senate Homeland Security and Governmental Affairs Committee, asked for information regarding when Rosenstein learned of the messages Strzok and Page exchanged, as well as whether the Justice Department knows of any similar messages Strzok sent or received during other investigations.

Johnson and Senate Judiciary Committee Chairman Chuck Grassley, R-Iowa, also sent a letter to Michael Horowitz, inspector general for the Justice Department, inquiring about the text messages Strzok and Page exchanged “that expressed anti-Trump political views.”

Strzok was one of the leaders of the FBI’s investigation into Hillary Clinton’s use of a private email server, and he participated in interviews with a number of Clinton’s top aides, including Huma Abedin and Cheryl Mills, as well as Clinton’s own interview with the FBI.

The longtime FBI investigator also reportedly edited a draft of former FBI Director Jim Comey’s statement on the probe into Clinton’s email use, changing the phrase “grossly negligent” to “extremely careless.”

In addition to his participation in the Clinton investigation, Strzok also played a role in special counsel Robert Mueller’s investigation into Russian meddling in the 2016 election. But Mueller removed Strzok from the probe over the summer after it was discovered he sent anti-Trump messages to Page.

The two were reportedly involved in an extramarital affair during the Clinton investigation.

Johnson said he wants to better understand Rosenstein’s awareness of the messages exchanged between Strzok and Page, as well as the Justice Department’s actions in response to the communicates.

Grassley asked FBI Director Christopher Wray for similar information regarding Strzok, including his involvement in drafting Comey’s statement, and messages he exchanged “containing unfavorable statements about Donald J. Trump or favorable statements about Hillary Clinton.”