Sen. Ron Johnson Ronald (Ron) Harold JohnsonThe Hill's 12:30 Report: Ginsburg lies in repose CHC leaders urge Senate to oppose Chad Wolf nomination Top GOP senators say Hunter Biden's work 'cast a shadow' over Obama Ukraine policy MORE (R-Wis.) requested Friday that the FBI release materials related to the bureau's interactions with Department of Justice (DOJ) official Bruce Ohr and former DOJ lawyer Michael Sussmann.

Johnson, the chairman of the Senate Homeland Security and Governmental Affairs Committee, sent a letter to FBI Director Christopher Wray asking him to share information on the FBI's interactions with both individuals.

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In his letter, Johnson cites "public reports," including a report from The Hill, that former FBI general counsel James Baker met with Sussmann, now an attorney with Perkins Coie. Perkins Coie retained research firm Fusion GPS in 2016 to research allegations that President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE colluded with Russia during the 2016 presidential election.

"Fusion GPS hired Christopher Steele — author of the Steele dossier — and Mr. Sussmann allegedly provided the FBI with information 'related to Russian interference in the election, hacking and possible Trump connections,' " the letter reads.

"According to separate reporting, the FBI met at least 12 times with Justice Department official Bruce Ohr, who 'began feeding information to the FBI from dossier author Christopher Steele in late 2016.' To better understand the FBI’s interactions with these two individuals, I request that you produce all communications and documents, including the FD-302s, memorializing the FBI’s communications with Michael Sussmann and Bruce Ohr," Johnson added.

Ohr became the target of intense scrutiny by conservatives earlier this year who argued that Ohr's ties to Fusion GPS through his wife, Nellie Ohr, and his contacts with former British spy Christopher Steele were evidence that there is bias against President Trump within the DOJ.

Glenn Simpson, co-founder of Fusion GPS, hired Steele to compile the so-called Steele dossier, which contains a series of salacious allegations about Trump’s ties to Russia. The dossier was paid for, in part, by Hillary Clinton Hillary Diane Rodham ClintonDemocratic groups using Bloomberg money to launch M in Spanish language ads in Florida The Hill's Campaign Report: Presidential polls tighten weeks out from Election Day More than 50 Latino faith leaders endorse Biden MORE's presidential campaign.

Trump, in August, said he would declassify a series of sensitive documents related to special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's Russia investigation into possible collusion between the Trump campaign and Moscow, including FBI reports of interviews with Bruce Ohr. Later that week he delayed the release of those documents, saying "key allies" raised concerns.

Bruce Ohr and Baker met with congressional investigators last month. Nellie Ohr is set to do so on Oct. 19.

Lawyers for Simpson told the head of the House Judiciary Committee on Thursday that his client will “invoke his constitutional rights not to testify,” despite a Republican-issued subpoena seeking to compel him to give a confidential deposition.

The attorneys blasted the committee's inquiry as part of a partisan probe aimed at undermining Mueller's investigation.

“The obvious — and at times explicitly stated — goal of this Committee is to discredit and otherwise damage witnesses to Russia’s interference in the 2016 election, all as part of an effort to protect a President who has sought to placate and curry favor with a hostile foreign power and who demands that the Justice Department stop investigating him,” they wrote.

CORRECTION: An earlier version of this story misstated who had signed on to Johnson's letter.