The former head of China's Centre for Disease Control played a key role in responding to the pandemic.
A top Chinese government scientist says nothing should be ruled out in the search to find the origins of COVID-19.
Professor George Gao - who was the head of China's Centre for Disease Control - played a central role in combating the pandemic and attempts to find out where it came from.
Many scientists believe the virus spread naturally from bats to humans. But others say there isn't enough evidence to rule out the possibility it first infected someone involved in research to better understand viruses in a laboratory.
China's government has repeatedly dismissed the idea that the disease could have originated from a laboratory in Wuhan, where COVID first surfaced.
But in an interview for the BBC podcast Fever: The Hunt for Covid's Origin, Professor Gao is much less forthright.
"You can always suspect anything. That's science. Don't rule out anything," he said.
Professor Gao added some kind of investigation into the Wuhan Institute of Virology had been carried out following the outbreak, noting the "lab was double-checked by the experts in the field."
While his department was not involved in this investigation and he had not seen the specific results, he had been told it was given a clean bill of health.
The podcast also hears from a Singapore-based scientist, Professor Wang Linfa, who was visiting the Wuhan Institute of Virology just as the coronavirus outbreak took hold.
He told the BBC a colleague at the institute had been worried about the possibility of a lab leak, but dismissed this.
Linfa said Professor Shi Zhengli, a professor with the same speciality at the WIV, told him she had "lost sleep for a day or two" as she was worried about the possibility that "there's a sample in her lab that she did not know of... [which could have] contaminated something, and got out."
But he says she checked samples and found they contained no evidence of the virus, or indeed any other virus close enough to have caused the outbreak.
Professor Wang believes that the evidence points overwhelmingly to the virus passing from animals to humans in a Wuhan market.