The U.K.’s The Sunday Times newspaper reported that a sample of the close relation was stored at the Wuhan Institute of Virology, known for its research on coronaviruses—the family of pathogens that COVID-19 coronavirus is a member of.

COVID-19 is caused by a coronavirus named SARS-CoV-2, not to be confused with the SARS disease behind an outbreak almost 20 years ago, which is triggered by another coronavirus called SARS-CoV.

President Donald Trump and Secretary of State Mike Pompeo have alleged SARS-CoV-2 emerged from a laboratory at the Wuhan Institute of Virology, in claims denied by its director. Scientists have also stated the claim is a “conspiracy theory.”

According to the Times investigation, six workers in China came down with severe pneumonia in spring 2012 after cleaning bat feces from an abandoned copper mine near Tongguan, Yunnan province.

The miners fell ill with symptoms similar to COVID-19, including a fever, cough, sore limbs, and breathing difficulties. Two men died initially. The four who survived men were tested for a raft of infections, but these came back negative.

At the time, doctors sent blood samples from the patients to the Wuhan Institute of Virology, where Shi Zhengli—a scientist dubbed “bat woman” due to her work on coronaviruses in these animals—works.

Four of the men were found to have antibodies for an unknown SARS-like coronavirus. One later died. The coronavirus was not named in the report.

The men died of a fungus according to a recent interview with Shi by Scientific American, but she said they would have eventually caught a coronavirus had the mine not been quickly shut.

In the year following the incident, Shi and colleagues headed to the mine, collected feces samples from 276 bats, and sent them to their Wuhan lab for storage and analysis.

The team published a paper in the journal Virologica Sinica in 2016, based on this work, stating that they had found a “new strain” of a SARS-like coronavirus named RaBtCoV/4991.

In February 2020, as SARS-CoV-2 was spreading around the world, Shi published an article in the journal Nature stating that the germ was closely related to a virus stored in their lab. The bat virus named RaTG13 shared 96 percent of its genetic make-up with SARS-CoV-2, found in Yunnan province in 2013, the paper stated.

The Sunday Times alleges RaTG13 is “almost certainly” the same as RaBtCoV/4991.

According to the newspaper, a database of bat viruses published by the Chinese Academy of Sciences lists RaTG13 and RaBtCoV/4991 as the same.

RaTG13 is also listed as found on July 24, 2013, and as one of the coronaviruses detailed in the 2016 mine paper. The Chinese Academy of Sciences is the parent body of the Wuhan Institute of Virology. The newspaper also reported that scientists in India and Austria found that part of the genetic makeup of the RaBtCoV/4991 published in the 2016 paper was a 100 percent match to RaTG13, and 98.7 percent to SARS-CoV-2.

Peter Daszak, president of the U.S.-based EcoHealth Alliance which works with the Wuhan Institute, told The Sunday Times RaTG13 was indeed discovered in the mine.

Regarding the name change, he said: “The conspiracy folks are saying there’s something suspicious about the change in name, but the world has changed in six years—the coding system has changed.”

Daszak said the sample from the mine was kept at the Wuhan lab for six years. But it disintegrated after the team tried to sequence the genome “in 2020, in early January or maybe even at the end of last year, I don’t know.”

Experts who spoke to The Sunday Times said the genetic difference between SARS-CoV-2 and RaTG13 mean it would take between 20 to 50 years for RatG13 to become COVID-19, while another stated it is possible it entered humans and adapted to cause the current pandemic.

Back in May, experts told Newsweek it is likely SARS-CoV-2 naturally evolved from a coronavirus from bats with a potential intermediary host.

However, Jeremy Rossman, honorary senior lecturer in virology at the University of Kent, told Newsweek at the time: “The exact origins of the virus and its jump into humans may never be conclusively proven.”

Rossman said Monday: “There are clearly some important and unresolved issues about the origins of COVID-19 and in the absence of transparency it is easy for conspiracy theories to grow. It is important to understand the provenance of the RaTG13/RaBtCoV/4991 strain of virus and its relation to the pneumonia cases in Kunming, as this will help us to better understand the evolution and pathology of SARS-CoV-2.

“However, the genetic differences between RaTG13 and SARS-CoV-2 are such that it is highly unlikely that an accidental release of the RaTG13 virus would have led to the current pandemic.”

Rossman said cooperation on an international scale is needed to stop the current pandemic. “Viral origins are clearly important but placing blame will not help us with containment. Unfortunately, without increased transparency from the Wuhan Institute of Virology and the Chinese government, it is unlikely that we have be able to lay these theories to rest any time soon,” he said.

Newsweek has contacted Wuhan Institute of Virology for comment.

This article has been updated with comment from Jeremy Rossman.