A World Health Organization (WHO) official has accused a Chinese ambassador of being "contradictory" after they said laboratories in the U.S. should be investigated regarding the origins of the COVID-19 pandemic.
It comes after a U.S. investigation into the virus' origins, announced by president Joe Biden earlier this year, came back inconclusive, according to The Washington Post on Wednesday, which cited two anonymous U.S. officials.
The report had been open to the possibility that the virus had leaked from a lab in China. On Tuesday this week, Chen Xu, China's ambassador to the U.N. Office in Geneva, wrote to WHO director-general Tedros Adhanom Ghebreyesus to reiterate the finding of the WHO-convened COVID origins study that took place earlier this year, and found the lab leak hypothesis to be "extremely unlikely".
That report was subject to criticism from governments around the world.
They expressed concern that it lacked access to complete data and the lab leak hypothesis has remained open.
Xu wrote: "If some parties are of the view that the 'lab leak' hypothesis remains open, it is the labs of Fort Detrick and University of North Carolina in the U.S. that should be subject to transparent investigation with full access."
In a WHO media briefing held on Wednesday, Michael Ryan, executive director of the WHO Health Emergencies Programme, said he found the call to investigate other countries' labs "difficult to understand" after a reporter raised Xu's comments.
Ryan said: "It is slightly contradictory if colleagues in China are saying that the lab leak hypothesis is unfounded in the context of China but we now need to go into laboratory investigations in other countries for leaks there.
"I find that difficult to understand, but very willing to engage with our Chinese colleagues to understand what exactly they mean by that statement."
He added that all hypotheses regarding the origins of the COVID pandemic "are still on the table" and that the WHO will follow wherever the leads take it.
Meanwhile, a group of medical experts from several institutions around the world co-authored an article in the journal Nature on Wednesday, warning that time was running out in terms of conducting scientific inquiry into the pandemic's origins.
The experts, who had been convened by the WHO in October last year as members of the joint WHO-China team tasked with understanding the origins of COVID, said the investigation has stalled and added that further delays would make further inquiry biologically impossible.