Two World Health Organization experts were heading to the Chinese capital on Friday to lay the groundwork for an investigation into the origins of the coronavirus pandemic.

An animal health expert and an epidemiologist will meet Chinese counterparts in Beijing to work out logistics, places to visit and the participants for a WHO-led international mission, the U.N. organization said.

A major issue will be to “look at whether or not it jumped from species to human, and what species it jumped from,” WHO spokesperson Dr. Margaret Harris said at a briefing in Geneva.

Scientists believe the virus may have originated in bats and was transmitted to another mammal such as a civet cat or an armadillo-like pangolin before being passed on to people.

A cluster of infections late last year focused initial attention on a fresh food market in the central Chinese city of Wuhan, but the discovery of earlier cases suggests the animal-to-human jump may have happened elsewhere.

In an effort to block future outbreaks, China has cracked down on the trade in wildlife and closed some markets, while enforcing strict containment measures that appear to have virtually stopped new local infections.

The WHO mission is politically sensitive, with the U.S. — the top funder of the U.N. body — moving to cut ties with it over allegations it mishandled the outbreak and is biased toward China.

“China took the lead in inviting WHO experts to investigate and discuss scientific virus tracing,” Chinese foreign ministry spokesperson Zhao Lijian said Friday.

In contrast, he said, the U.S. “not only announced its withdrawal from the World Health Organization, but also politicized the anti-epidemic issue and played a buck-passing game to shift responsibilities.”

More than 120 nations called for an investigation into the origins of the virus at the World Health Assembly in May. China has insisted that WHO lead the investigation and for it to wait until the pandemic is brought under control. The U.S., Brazil and India are continuing to see an increasing number of cases.

The last WHO coronavirus-specific mission to China was in February, after which the team’s leader, Canadian doctor Bruce Aylward, praised China’s containment efforts and information sharing. Canadian and American officials have since criticized him as being too lenient on China.

An Associated Press investigation showed that in January, WHO officials were privately frustrated over the lack of transparency and access in China, according to internal audio recordings. Their complaints included that China delayed releasing the genetic map, or genome, of the virus for more than a week after three different government labs had fully decoded the information.

Privately, top WHO leaders complained in meetings in the week of Jan. 6 that China was not sharing enough data to assess how effectively the virus spread between people or what risk it posed to the rest of the world, costing valuable time.

(AP)