(AP) — A global team of researchers arrived Thursday in the Chinese city where the coronavirus pandemic was first detected to conduct a politically sensitive investigation into its origins amid uncertainty about whether Beijing might try to prevent embarrassing discoveries.

The group sent to Wuhan by the World Health Organization was approved by President Xi Jinping’s government after months of diplomatic wrangling that prompted an unusual public complaint by the head of WHO.

Scientists suspect the virus that has killed more than 1.9 million people since late 2019 jumped to humans from bats or other animals, most likely in China’s southwest. The ruling Communist Party, stung by complaints it allowed the disease to spread, has suggested the virus came from abroad, possibly on imported seafood, but international scientists reject that.

They will undergo a two-week quarantine as well as a throat swab test and an antibody test for COVID-19, according to CGTN, the English-language channel of state broadcaster CCTV. They are to start working with Chinese experts via video conference while in quarantine.

The team includes virus and other experts from the United States, Australia, Germany, Japan, Britain, Russia, the Netherlands, Qatar and Vietnam.

A government spokesman said this week they will “exchange views” with Chinese scientists but gave no indication whether they would be allowed to gather evidence.

China rejected demands for an international investigation after the Trump administration blamed Beijing for the virus’s spread, which plunged the global economy into its deepest slump since the 1930s.

After Australia called in April for an independent inquiry, Beijing retaliated by blocking imports of Australian beef, wine and other goods.

One possibility is that a wildlife poacher might have passed the virus to traders who carried it to Wuhan, one of the WHO team members, zoologist Peter Daszak of the U.S. group EcoHealth Alliance, told The Associated Press in November.

A single visit by scientists is unlikely to confirm the virus’s origins; pinning down an outbreak’s animal reservoir is typically an exhaustive endeavor that takes years of research including taking animal samples, genetic analysis and epidemiological studies.

“The government should be very transparent and collaborative,” said Shin-Ru Shih, director at the Research Center for Emerging Viral Infections at Taiwan’s Chang Gung University.

The Chinese government has tried to stir confusion about the virus’s origin. It has promoted theories, with little evidence, that the outbreak might have started with imports of tainted seafood, a notion rejected by international scientists and agencies.