The World Health Organization's (WHO) top emergency expert said on Friday the search for the origin of the coronavirus was being "poisoned by politics", days after US President Joe Biden ordered aides to find answers.
Since the virus outbreak that emerged in the central Chinese city of Wuhan in December 2019, scientists have been trying to solve the puzzle of where the virus originated.
"We would like for everyone out there to separate if they can, the politics of this issue from the science. This whole process is being poisoned by politics," Mike Ryan told reporters.
A WHO-led team spent four weeks in and around Wuhan with Chinese researchers and said in a report in March that the virus had probably been transmitted from bats to humans through another animal.
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It said that "introduction through a laboratory incident was considered to be an extremely unlikely pathway".
But many politicians and a number of scientists are not satisfied.
Biden on Wednesday ordered aides to find answers to the virus' origin, saying US intelligence agencies were pursuing rival theories, potentially including the possibility of a laboratory accident in China.
The United States on Thursday called on the WHO to carry out a second probe.
"Every country and every entity is free to pursue their own particular theories of origin, it's a free world," Ryan said. "WHO is a member state organisation and we seek to work with all of our member states to seek answers collectively."
Maria Van Kerkhove, WHO's the technical lead on Covid-19, added that the issue required multiple missions and would take time.