Newly reported US intel found three Wuhan lab workers fell ill with COVID-19 symptoms in fall 2019.
Some experts have disputed a WHO inquiry's conclusion that dismissed a coronavirus lab-leak theory.
The US intel reportedly emerged at the end of the Trump administration, which embraced the theory.
US intelligence found that three researchers at a lab in Wuhan, China, became sick with COVID-19 symptoms in November 2019 and sought hospital care, The Wall Street Journal reported Sunday.
News of the information, which The Journal said was included in a US intelligence report, comes as some experts call for a reevaluation of whether the coronavirus pandemic was triggered by an accident at the Wuhan Institute of Virology.
The Journal said the new details added to information from a State Department fact sheet issued in the last days of President Donald Trump's administration. It added that officials familiar with the report did not agree on the strength of the evidence found.
Earlier this year, a team from the World Health Organization spent a month in Wuhan investigating the origin of the coronavirus and concluded that the virus most likely jumped from bats to people through an intermediary animal.
The group said a lab leak was "extremely unlikely."
It was known previously that some researchers at the Wuhan lab fell ill. In March, Marion Koopmans, a Dutch virologist, told NBC News the illness of lab workers could be attributed to regular seasonal illnesses such as the flu.
WHO, however, also said it did not have access to all the necessary information. That has prompted some experts to be wary of the findings and demand more investigations into the virus' origin, including the possibility that it leaked from the Wuhan lab, which studies coronaviruses.
November 2019 is in line with when experts believe the COVID-19 virus began circulating.
China has consistently denied the coronavirus escaped from a lab. The lab, however, hasn't released raw data or records on its work with coronaviruses in bats.
A spokeswoman for the National Security Council told The Journal that the Biden administration still had questions on the origin of the virus and that plausible theories should be investigated.
"We're not going to make pronouncements that prejudge an ongoing WHO study into the source of SARS-CoV-2," the spokeswoman said. "As a matter of policy we never comment on intelligence issues."
On Monday, the director of the institute's Wuhan National Biosafety Laboratory, Yuan Zhiming, told a Chinese state media outlet, the Global Times, that The Journal's report was "a complete lie."
"Those claims are groundless," Yuan said. "The lab has not been aware of this situation [sick researchers in autumn 2019], and I don't even know where such information came from."
Read the original article on Business Insider