A former top Chinese government scientist told BBC News that the potential of the Covid virus leaking from a laboratory should not be ruled out.

Prof George Gao, the head of China’s Centre for Disease Control (CDC), was instrumental in the pandemic response and efforts to trace its roots.

The Chinese government denies that the sickness originated in a Wuhan facility.

Prof. Gao, on the other hand, is more reserved.

Prof Gao states in an interview for the BBC Radio 4 podcast Fever: The Hunt for Covid’s Origin, “You can always suspect anything.” That’s how science works. “Don’t rule anything out.”

Prof Gao, a world-renowned virologist and immunologist, is currently vice-president of the National Natural Science Foundation of China, having retired from the CDC last year.

Prof Gao also informs the BBC that a formal investigation of the Wuhan Institute of Virology (WIV) was conducted, which could indicate that the Chinese government took the lab leak idea more seriously than public pronouncements indicated.

“The government organized something,” he claims, adding that his own department, the China CDC, was not involved.

We asked him to clarify whether this meant that another arm of government conducted a formal search of the WIV – one of China’s premier national laboratories that has spent years researching coronaviruses.

“Yeah,” he says, “that lab was double-checked by experts in the field.”

It’s the first time an official investigation has been acknowledged, but while Prof Gao hasn’t seen the results, he has “heard” that the lab was granted a clean bill of health.

“I believe their conclusion is that they are adhering to all protocols.” They haven’t discovered any misconduct.”