Mr Johnson urged officials to ramp up their investigation into the origin of the pandemic virus.
He told CBC: “I’ve got an open mind on this, but I’ll be clear with you — so far, the stuff I’ve seen does not suggest that the number one candidate for this is a lab leak.
“So the stuff I’ve seen suggests that at the moment, the number one suspect for the origin of this disease is still a zoonotic disease that occurred as a result of the farming of wild animals in some way.”
He continued: “That is what the WHO still says as well. But I am not going to exclude any possibility.
“I’m reading a lot of interesting stuff at the moment about the possibility that there was some virus escaping from a lab. I think we’ve got to keep an open mind.”
On Sunday, it was revealed that British intelligence services are now regarding the theory that COVID-19 originated in and was leaked from a lab in Wuhan as “feasible”.
Previously, intelligence services believed there was only a “remote” chance the virus had originated in the lab.
Beijing has repeatedly denied that the Wuhan Institute of Virology is the source of the virus that has caused more than 3.5 million deaths.
China’s foreign ministry accused the US of “political manipulation and blame shifting”.
The controversial theory that Covid came from a lab in Wuhan, where researchers study the coronavirus in bats, emerged early on in the pandemic, largely due to the backing of then-US President Donald Trump.
MPs in the UK are demanding a fresh investigation, with the Conservative MP Tom Tugendhat telling the Sunday Times: “The silence coming from Wuhan is troubling.
“We need to open the crypt and see what happened to be able to protect ourselves in the future.
“That means starting an investigation, along with partners around the world and in the WHO.”