Sen. Ron Johnson and Sen. Rand Paul are accusing the HHS of stonewalling on the origin of the coronavirus and have sent multiple letters requesting documents. 

On Thursday, Johnson sent a letter to Becerra following up on a previous letter from June requesting emails between health officials and scientists related to a Wuhan lab that received United States research funding.

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Johnson told Fox News that the U.S. government provided 200 pages of documents, but the redactions made it impossible to gather proper context. 

"They do not feel like they have to be honest with Congress and transparent with the American public," Johnson told Fox News. "They release information that’s so fully redacted you really can’t use it for legitimate oversight."

In the August 19 letter, Johnson asks Becerra for unredacted documents from National Institute of Allergy and Infectious Diseases official Ping Chen concerning her report on a visit to the Wuhan Institute of Virology.

"Based on other documents in our possession, including a January 19, 2018 State Department cable regarding safety concerns at the WIV, we are concerned that HHS has redacted important information potentially relating to these safety issues," the letter says. 

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The letter says that based on some correspondences from April 2020 that have been made public, "it appears that Chen’s November 2017 report partially served as the basis for the January 2018 cable that raised safety concerns about the Wuhan lab."

The letter continues, "However, because of HHS’s redactions and incomplete document production, it is unclear whether Chen raised similar safety concerns to her colleagues in the enclosed email chain regarding her trip to the Wuhan lab. If Chen did raise safety concerns about the Wuhan lab to NIAID and National Institutes of Health officials as early as November 2017, it is unclear what actions, if any, those officials took."

The letter calls for a "complete unredacted copy of Ping Chen’s 2017 report" and "all unredacted communications referring or relating to her report.

"The fact that we’re not getting this information, to me, just smacks of a cover-up," Johnson said. "Why is it the NIH, HHS, NIAID, the organization that Fauci has, why aren't they being completely transparent? What do they have to cover up?"

Johnson called on Senate Homeland Security & Governmental Affairs Committee Chairman Gary Peters, a Democrat,  to utilize the committee’s subpoena power to look at the information on a "bipartisan basis."

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"Particularly the Anthony Fauci emails, those occurred during a previous administration, a Republican administration, those are information on gain of function," Johnson added. "What do NIAID know about the lack of protocols and safety at a bio lab that they were funding research at? What do they know and when did they know it?"

"That’s information the American government needs to know about what certain government agencies are doing, particularly involving something as dangerous as gain of function research," Johnson said. 

As the lab-leak theory has gained credibility after being widely dismissed in the press last year, there's more attention being paid to monies given to the Wuhan Institute of Virology, known for its bat coronavirus research and so-called "gain of function" methods, which involves manipulating viruses to make them more infectious for research.

Republicans on the House side have also been trying to press the federal government for answers involving gain of function research at the Wuhan lab that many believe was the site where the coronavirus originated. 

Last month, Reps. Chip Roy, R-Texas, and Bill Posey, R-Fla., led a letter – first obtained by Fox News – to the nation's top infectious disease expert in which they accuse him of appearing to "mislead the American people on the origins of COVID-19 and gain-of-function research."

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"He testified before the Senate that risky gain-of-function research was not occurring in Wuhan, yet in his now-public emails, sends an urgent message to his deputy on gain-of-function," Roy told Fox News Wednesday. "His emails also implicate him in having influence over a paper that called the lab leak theory implausible. 

"The American people deserve answers about what Fauci knew and when he knew it; we must investigate this and see wherever the truth leads us."

The group of 13 lawmakers fired off a series of specific questions to Fauci about his emails, which were recently published by news outlets thanks to Freedom of Information Act (FOIA) requests. They suggest that Fauci's email communications contradict his public statements that the National Institutes of Health (NIH) did not fund so-called "gain-of-function" research at a Wuhan virology lab.

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Fauci, the director of the National Institute of Allergy and Infectious Diseases, has repeatedly denied any NIH money went to such research in Wuhan, but his organization has given millions of dollars in grant money to the EcoHealth Alliance, a research nonprofit that funneled at least $600,000 to Wuhan coronavirus research.

Marisa Schultz contributed to this report