Sen. Tom Cotton, R-Ark., criticized "reporters [and] activists in white lab coats" for dismissing a theory linking the origins of COVID-19 to a Wuhan, China-based virology lab.

Cotton and other Republican lawmakers including Sen. Ted Cruz, R-Texas, faced backlash from reporters and pundits in 2020 after highlighting the theory as a potential explanation for how the virus that shut down countries across the globe began in Wuhan.

But reporters and outlets are now walking back their initial dismissals of the theory after officials revealed over the weekend that several workers at the Wuhan Institute of Virology fell ill in mid-November 2019, about a month before the first COVID-19 case was reported in the Chinese city. 

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"The lab-leak hypothesis was always reasonable, but reporters & activists in white lab coats nonetheless spent the better part of a year denouncing it as a ‘conspiracy theory,’" Cotton tweeted late Tuesday. "They were wrong. But that’s not what’s most important now. What’s important is truth & accountability."

Cotton directed his followers to a Sunday Wall Street Journal report citing previously undisclosed U.S. intelligence documents that found some of the Wuhan Institute of Virology workers who fell ill in 2019 required hospital care, lending weight to what some have dubbed the "lab-leak theory." 

He also pointed to a Hudson Institute event in which fellows and journalists discussed the origins of the virus and reports detailing unsafe conditions of the Wuhan virology lab.

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He added that the U.S. needs to open a "full, impartial investigation" into COVID-19's origins with a focus on "Wuhan labs."

'The Wuhan Institute of Virology [and] Wuhan CDC need to open their doors [and] databases for a full audit of their research—especially dangerous gain-of-function research," he tweeted. "The [Chinese Communist Party] needs to stop obstructing investigators, destroying evidence, and telling ridiculous lies."

One State Department official who spoke to Fox News and worked at the State Department during the Trump administration claimed to have been in touch with foreign government contacts when Wuhan lab workers first became sick and said colleagues also had been in communication with contacts about the issue. 

The State Department told Fox News it would not comment on "purported intelligence matters."

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The State Department acknowledged in January 2021 the "United States government has reason to believe that several researchers inside the WIV became sick in autumn 2019." It found that they'd experienced symptoms consistent with both COVID-19 "and common seasonal illness."

The Wuhan Institute of Virology, which is one of China’s top virus research labs, built an archive of genetic information about bat coronaviruses after the 2003 outbreak of Severe Acute Respiratory Syndrome and has faced criticism over its transparency throughout the pandemic.

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The Journal reported that the veracity of the intelligence is being debated by current and former officials. At least one told the paper that further analysis is needed since the evidence was provided by foreign contacts. Another source told the paper that the evidence seems to be spot on and "was of exquisite quality."

The paper reported that China has denied any allegation that the virus was somehow leaked from the lab. China accused the U.S. on Sunday of continuing its effort to "hype the lab leak theory."

Fox News' Edmund DeMarche and Rich Edson contributed to this report.