(NewsNation) — A special panel formed by House Republicans investigating the origins of the coronavirus met again Tuesday to tackle the question: Where did the virus that’s killed nearly 7 million people worldwide come from?

That question was also being asked years ago by Jamie Metzl, one of the first people who suggested the virus might have been the result of an accidental lab leak.

Metzl, who served on a World Health Organization advisory committee, agreed with congressional testimony, saying Tuesday on “Elizabeth Vargas Reports” there is a “mountain of circumstantial evidence” that points to a lab leak.

“Everything, at least in my estimation, is leaning towards the lab accident,” Metzl said.

The U.S. intelligence community remains divided on the origin, while top U.S. health officials, including Dr. Anthony Fauci, maintain a natural transmission is still the likeliest explanation.

Fauci told NewsNation earlier this month that while “accumulating evidence” points to a natural origin, everyone must keep an open mind because of China’s unwillingness to provide more information.

“We may not ever get (definitive proof), and that’s one of the frustrating things,” Fauci said.

Witnesses at Tuesday’s hearing included former Director of National Intelligence John Ratcliffe, who said, “a lab leak is the only explanation credibly supported by our intelligence, our science and our common sense.”

The hearing centered on China’s effort to block access to and information on what was being researched at a laboratory in Wuhan, where a large outbreak of COVID-19 began in 2019. Also in Wuhan is a seafood market where researchers suggest the virus might have first spread.

Fauci’s comments came on the heels of a new study published this month that shows large amounts of the virus were mixed in with genetic material from racoon dogs at an outdoor wet market in Wuhan.

The research focused on swabs taken in Wuhan in the early days of the pandemic. Chinese researchers confirmed DNA from raccoon dogs and other animals was found in COVID-19 samples, especially from one corner of the wet market where exotic wildlife was sold.

The first version of the study was published in 2022 and did not mention finding any genetic material from racoon dogs in the swabs, The New York Times reported.

The study added to the raging debate over whether the virus came from a lab leak or natural transmission. However, it does not prove that the virus originated there.

Metzl admonished China for hiding evidence that could unlock the answers.

“China has systematically destroyed samples, hidden records, imprisoned Chinese journalists for asking the most basic questions,” Metzl said. “They have a gag order to this day preventing Chinese scientists from saying or writing anything about pandemic origins without prior government approval, and they’ve done everything in their power to block an international investigation.”

NewsNation writers Taylor Delandro and Cassie Buchman contributed to this report.