As head of China's Centre for Disease Control (CDC), Prof George Gao played a key role in the pandemic response and efforts to trace its origins, reports BBC.

China has so far rejected any claims that the virus had originated from a Wuhan laboratory.

In an interview for the BBC Radio 4 podcast Fever: The Hunt for Covid's Origin, Prof Gao says: "You can always suspect anything. That's science. Don't rule out anything."

A world-leading virologist and immunologist, Gao is now vice-president of the National Natural Science Foundation of China after retiring from the CDC last year.

In a possible sign that the Chinese government may have taken the lab leak theory more seriously than its official statements suggest, Gao also tells the BBC some kind of formal investigation into the Wuhan Institute of Virology (WIV) was carried out.

"The government organised something," he says, but adds that it did not involve his own department, the China CDC.