A team of investigators led by the World Health Organization (WHO) arrived on Tuesday at an animal health facility in China’s central city of Wuhan in the search for clues about the origins of the COVID-19 pandemic.

The independent team has already visited key hospitals, the regional disease control centre and the city’s Huanan seafood market, where the first cluster of infections was believed to have originated late in 2019.

The trip was going “really well, excellent,” one of its members, Peter Daszak, president of the EcoHealth Alliance, told Reuters on Tuesday, responding to a query just before entering the animal health centre.

The centre in the province of Hubei, which fights epidemic diseases in animals, could provide information on how a coronavirus endemic in horseshoe bats in southwest China might have crossed into humans, possibly via an intermediary species.

Peter Ben Embarek, the WHO’s top expert on “zoonotic” diseases that originate in animals, was among the team members clad in white suits of personal protective equipment spotted within the centre’s premises.

A worker, also wearing protective gear, disinfected the road outside after the team had entered.

On Monday, the WHO’s top emergency official, Mike Ryan, said the investigation might not find all the answers to the origins of COVID-19, describing the mission as a “detective story” that continued to raise new questions.

He also criticised those who have said they would not accept the team’s findings.

“It deserves the support of the international community and it deserves to be able to finish its work,” he added.