The Republican chairmen of the House Oversight Committee and the subcommittee on the coronavirus pandemic requested information from several people, including Dr. Anthony Fauci, surrounding the hypothesis that the coronavirus leaked accidentally from a Chinese lab.

“This investigation must begin with where and how this virus came about so that we can attempt to predict, prepare or prevent it from happening again,” Rep. Brad Wenstrup, R-Ohio, chair of the virus subcommittee, said in a statement.

Rep. James Comer, R-Tenn., chairman of the oversight committee, added that Republicans will “follow the facts” and “hold U.S. government officials that took part in any sort of cover-up accountable.”

The letters to Fauci, National Intelligence Director Avril Haines, Health Secretary Xavier Beccera and others are the latest effort by the new Republican majority to make good on promises made during the 2022 midterms campaign.

Wenstrup, who is also a longtime member of the House Intelligence Committee, has accused U.S. intelligence of withholding key facts about its investigation into the coronavirus. Republicans on the committee last year issued a staff report arguing that there are “indications” that the virus may have been developed as a bioweapon inside the Wuhan Institute of Virology.

That would contradict a U.S. intelligence community assessment released in unclassified form in August 2021 that said analysts do not believe the virus was a bioweapon, though it may have leaked in a lab accident.

The letters sent Monday do not require the cooperation of recipients. But in announcing the Republican staff report in December, Wenstrup said that lawmakers would issue subpoenas if potential witnesses didn’t cooperate.

Initially dismissed by most public health experts and government officials, the hypothesis that COVID-19 originated from an accidental lab leak began to receive scrutiny after President Joe Biden ordered an investigation into the matter in May 2021.

The 90-day review was meant to push American intelligence agencies to collect more information and review what they already had. Former State Department officials under President Donald Trump had publicly pushed for further investigation into virus origins, as had scientists and the World Health Organization.

Many scientists, including Fauci, who until December served as Biden’s chief medical adviser, say they still believe the virus most likely emerged in nature and jumped from animals to humans, a well-documented phenomenon known as a spillover event. Virus researchers have not publicly identified any key new scientific evidence that might make the lab-leak hypothesis more likely.

But Republicans have accused Fauci of lying to Congress when he denied in May that the National Institutes of Health funded “gain of function” research — the practice of enhancing a virus in a lab to study its potential impact in the real world — at a virology lab in Wuhan, China. Sen. Ted Cruz, R-Texas, even urged Attorney General Merrick Garland to appoint a special prosecutor to investigate Fauci’s statements.

Fauci, who served as the country’s top infectious disease expert under both Republican and Democratic presidents, has called the GOP criticism nonsense.

Cruz and Sen. Rand Paul, R-Ky., have previously said that an October 2021 letter from NIH to Congress contradicts Fauci. But no clear evidence or scientific consensus exists that “gain of function” research was funded by NIH, and there is no link between U.S.-funded research to the emergence of COVID-19. NIH has repeatedly maintained that its funding did not go to such research involving boosting the infectivity and lethality of a pathogen.

Nonetheless, Fauci indicated in November that he would “cooperate fully and testify” if Republicans followed through with their plans to investigate COVID’s origin.

“I have no trouble testifying — we can defend and explain everything that we’ve said,” he told reporters during a White House briefing last year.