Carlson's comments come after a previously undisclosed U.S. intelligence report revealed that three staffers at a Wuhan virology lab became sick with Covid-like symptoms weeks before China disclosed the virus outbreak to the world.
"The U.S. government has reason to believe that several researchers inside the WIV became sick in autumn 2019, before the first identified case of the outbreak, with symptoms consistent with both Covid-19 and common seasonal illnesses".
Information about the researchers was published in the Wall Street Journal on Sunday.
The origin of the virus is hotly contested.
When Dr Fauci was asked at an event whether he was still confident that the coronavirus developed naturally he said: "I am not convinced about that, I think we should continue to investigate what went on in China until we continue to find out to the best of our ability what happened".
This reporting adds a new level of detail to the information put out in a State Department fact sheet previous year, which said the USA had confirmed that researchers at the Wuhan Institute of Virology had fallen ill.
In April 2020, NBC News reported that the US had indications as far back as November of a possible health crisis in Wuhan.
A joint study into the origins of Covid-19 by the World Health Organization and China published at the end of March said it was "extremely unlikely" that it had escaped from a lab.
CDC relaxes mask-wearing rules for fully vaccinated people
Walensky said if you develop coronavirus symptoms, you should put your mask back on and get tested right away. "But any other time, if you're vaccinated and you're outside, put aside your mask", Fauci said .
However, most scientists say they have seen nothing to corroborate the US military lab origin theory.
"We continue to have serious questions about the earliest days of the COVID-19 pandemic, including its origins within the People's Republic of China", said a spokeswoman for the National Security Council.
TUCKER Carlson accused Anthony Fauci of lying about the origin of Covid-19 after a shocking report pointed to a Wuhan lab "leak".
"Phase 2 of the COVID origins study must be launched with terms of reference that are transparent, science-based, and give global experts the independence to fully assess the source of the virus and the early days of the outbreak", US health secretary Xavier Becerra said in a video message to the annual ministerial meeting of the World Health Organization.
USA agencies are concerned that World Health Organization representatives have been unable to conduct independent investigations inside China into COVID-19's origins, and are therefore wary of World Health Organization findings, one US government source briefed on these investigations said.
The New York Time's Maggie Haberman is blaming former President Donald Trump and former Secretary of State Mike Pompeo for the corporate media's reckless inability to seriously cover the Wuhan lab leak theory early in 2020.
The WHO, which opened its annual ministerial assembly on Monday, has not announced any follow-up to the Wuhan mission but member states may raise concerns in speeches to the week-long forum.
Since then, more than 167 million cases and 3.4 million deaths have been reported worldwide.
Speaking to the WHO on Tuesday, US Secretary for Health and Human Services Xavier Becerra did not mention China by name.