The coronavirus is unlikely to have leaked from a Chinese lab and is more likely to have jumped to humans from an animal, a World Health Organization expert said Tuesday.

WHO food safety and animal diseases expert Peter Ben Embarek made the assessment at the end of a visit to the central Chinese city of Wuhan, where a team of scientists is investigating the possible origins of the virus that causes COVID-19. The first cases were discovered in the city in December 2019.

The Wuhan Institute of Virology has collected extensive virus samples, leading to allegations that it may have caused the original outbreak by leaking the virus into the surrounding community. China has strongly rejected that possibility and has promoted other theories that the virus may have originated elsewhere. The team is considering several theories for how the disease first ended up in humans.

"Our initial findings suggest that the introduction through an intermediary host species is the most likely pathway and one that will require more studies and more specific, targeted research," Embarek said.

"However, the findings suggest that the laboratory incidents hypothesis is extremely unlikely to explain the introduction of the virus to the human population."

The WHO team draws on experts from 10 countries. Its mission is intended to be an initial step delving into the origins of the virus, which is believed to have originated in bats before being passed to humans through another species of wild animal, such as a pangolin or bamboo rat, which is considered an exotic delicacy by some in China.

Transmission through the trade in frozen products was also a likely possibility, Embarek said.

Another member of the WHO team told The Associated Press late last week that they enjoyed a greater level of openness than they had anticipated, and that they were granted full access to all sites and personnel they requested.

That expert, British-born zoologist Peter Daszak, said the team looked into issues including what the first cases were, the link with animals and what, if any, the role that imports of frozen food may have played — a theory that China has long put forward.

The visit by the WHO team took months to negotiate after China only agreed to it amid massive international pressure at the World Health Assembly meeting last May. Beijing has continued to resist calls for a strictly independent investigation.

Chinese authorities have kept a tight hold on information about the possible causes of the pandemic that has now killed more than 2.3 million people worldwide.