The Covid-19 virus may have originated from humans, a Chinese scientist has claimed.

The genetic sequences of viral samples taken from the Huanan Seafood Market in Wuhan – thought to be the ground zero site of the pandemic – were “almost identical” to those of patients infected with the coronavirus, suggesting that Covid-19 may have originated from humans, said Tong Yigang of the Beijing University of Chemical Technology.

Tong, who was speaking at a press conference held by the Chinese State Council regarding research into the origin of the virus, said more than 1,300 environmental and frozen animal samples had been taken at the market between January 2020 and March 2020, and researchers had isolated three strains of virus from the environmental samples.

He also said there was not yet sufficient evidence to back up recent studies that had suggested racoon dogs were the origin of the Covid-19 virus.

Speaking at the same event, a Chinese Center for Disease Control and Prevention (CDC) researcher, Zhou Lei, called for global scientific collaboration in tracing the origins of the virus, saying that the site where Covid-19 was first discovered was not necessarily where it originated.

China has in the past been heavily criticized for blocking international investigations into the origins of the virus. Earlier this week the World Health Organization said it still did not have key data from China about the beginnings of the outbreak, a lack of disclosure the head of its program on emerging diseases said was “simply inexcusable.”

However, China repeatedly maintains that it has been transparent and cooperative with the WHO.

Debates surrounding the origins of the virus reemerged recently following an assessment last month by the US Department of Energy it was most likely the result of an accident from a laboratory. But the US agency also marked it as a “low confidence” determination

On Saturday, Zhou refuted the lab leak theory, saying it is “extremely unlikely.”