The World Health Organisation (WHO) mission to China to unearth the origins of the coronavirus has failed to identify the animal source, scientists said Tuesday.

Experts believe the disease, which has gone on to kill more than 2.3 million people worldwide, originated in bats and could have been transmitted to humans via another mammal. While transmission from animals was the likely route, so far "the reservoir hosts remain to be identified", Liang Wannian, head of the China team said. He also said there was "no indication" the sickness was in circulation in Wuhan before December 2019 when the first official cases have been recorded.

He added that studies showed the virus "can be carried long-distance on cold chain products," appearing to nudge towards the possible importation of the virus -- a theory that has abounded in China in recent months.

WHO foreign expert Ben Embarak, who was based in the WHO's Beijing office for two years from 2009, backed up the assertion saying there was no evidence of "large outbreaks in Wuhan" before then.

The mission is a diplomatically knotty one, which was trailed before it began by fears of a whitewash, with the US demanding a "robust" probe and China firing back with a warning not to "politicise" the investigation. The experts spent one month in China, two weeks in quarantine and the same again on fieldwork.

But, already over a year after the virus emerged, some of it was of questionable relevance to their stated aim of finding the virus source, including a visit to a propaganda exhibition celebrating China's recovery from the pandemic. The group spent just an hour at the seafood market where many of the first reported clusters of infections emerged over a year ago. They also appeared to spend several days inside their hotel, receiving visits from various Chinese officials without going out into the city.

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