The theory of a leak from a Chinese laboratory being the cause of the Covid-19 outbreak is a politically motivated lie according to China.
The lab leak theory has nothing to do with science, according to the Chinese foreign ministry spokesman.
"We always supported and participated in science-based global virus tracing but we firmly opposed any forms of political manipulation."
There was a renewed focus on the data from China, where the first case of the disease was reported in late 2019.
On Thursday, the WHO said in a report that all available data showed the novel coronaviruses that caused Covid-19 probably came from animals, most likely bats.
It remains important to consider all reasonable scientific data when evaluating the possibility of the introduction of sars-coV-2 to humans.
Key pieces of data are still missing, and it's not possible to know how the virus was transmitted to humans.
The director general of the UN's top health agency wrote to the Chinese government twice in February this year to get more information, and China gave some data on request.
It is important for scientists to know what happened in the year 2019. Political wrangling between China and a number of western countries has hampered investigations into the origins of the Pandemic.
Time is running out for experts. Maria Van Kerkhove, a senior WHO official, said on Thursday that the longer it took, the harder it became.
"We owe it to ourselves, we owe the millions of people who died and the billions of people who were infections."
In the last few months, the WHO has become more vocal about China's method in dealing with the Pandemic. It said last month that Beijing's "zero- Covid" policy was unsustainable due to increased knowledge of the virus and the cost to the economy and civil rights. The criticism was rejected by China as irrational.
The Associated Press contributed.