Two experts from the World Health Organization will spend the next two days in Beijing to begin probe into the COVID-19 pandemic origin, AP reported.

According to the WHO, an animal health expert and an epidemiologist will meet their Chinese counterparts to work out logistics, places to visit, and the participants for a WHO-led mission.

Scientists believe that the virus may have come from bats, and then was transmitted through another mammal, such as a civet or an armadillo, before being passed on to people.

The WHO mission is politically sensitive, as the US, the organization’s main sponsor, seeks to break ties with it amid allegations the WHO mishandled the outbreak and is biased toward Beijing.

Over 120 countries called for a probe into the COVID-19 origin at the World Health Assembly in May. China insists that the WHO lead the investigation and wait for the pandemic to be brought under control.