Experts believed COVID-19 could have been engineered and leaked from a lab in the early days of the pandemic, but later concluded that the origin theory was not plausible, newly released emails to Dr. Anthony Fauci show.

In an email to Dr. Fauci sent on January 31 last year, Kristian G. Andersen of the Scripps Research Institute told the National Institute of Allergy and Infectious Diseases director that some of SARS-CoV-2’s features “(potentially) look engineered.”

But he also noted that “unusual features of the virus” made up a “really small part” of the genome, quantifying the features as less than 0.1 percent of the genome.

“We have a good team lined up to look very critically at this, so we should know much more at the end of the weekend,” Andersen told Fauci in an chain of emails obtained by BuzzFeed News through a Freedom of Information Act request.

Wuhan Institute of Virology
This general view shows the Wuhan Institute of Virology in Wuhan, in China’s central Hubei province on February 3, 2021.
Hector Retamal/AFP via Getty Images

“I should mention that after discussions earlier today, Eddie, Bob, Mike, and myself all find the genome inconsistent with expectations from evolutionary theory,” the expert added. “But we have to look at this much more closely and there are still further analyses to be done, so those opinions could still change.”

Andersen and his team later published an article in Nature Medicine, a peer-reviewed journal, which said they believed it was not plausible that COVID-19 was engineered and leaked from a laboratory.

“Although the evidence shows that SARS-CoV-2 is not a purposefully manipulated virus, it is currently impossible to prove or disprove the other theories of its origin described here,” the article read. “However, since we observed all notable SARS-CoV-2 features… in related coronaviruses in nature, we do not believe that any type of laboratory-based scenario is plausible.”

The paper later added that more scientific data “could swing the balance of evidence to favor one hypothesis over another.” Newsweek has contacted Andersen for further comment.

Posting on social media on Tuesday night, the expert confirmed that his team “seriously considered” the lab leak theory to be a possibility, but noted that “extensive analysis” and new data led to the different conclusion in their paper.

“What the email shows, is a clear example of the scientific process,” he tweeted about his January 31 email to Dr. Fauci.

The email was released after The Wall Street Journal obtained an intelligence report that claimed staff at the Wuhan Institute of Virology in China had shown “symptoms consistent with both COVID-19” and seasonal flu in late 2019, around the time of the outbreak.

Revelations in the State Department fact sheet have prompted speculation about the possible origins of COVID-19, and sparked President Joe Biden to order U.S. agencies to investigate where the coronavirus originated.