More than three years after the global coronavirus pandemic outbreak, conflicting information from the heads of China and the United States’ Center for Disease Control and Prevention continues to emerge.

George Gao, China’s former head for the CDC said Friday there is no evidence that COVID-19 came from an animal and jumped to humans. Gao served as head of China’s CDC at the end of 2019 when coronavirus first emerged from Wuhan, China.

“Even now, people think some animals are the host or reservoir,” George Gao said at a summit in London. “Cut a long story short, there is no evidence which animals (were) where the virus comes (from).”

Dr. Anthony Fauci told CNN in an interview over the weekend that a lab leak could still be considered a “natural occurrence.” Fox News reports that the World Health Organization has said that all hypotheses for the origins of COVID-19 remain on the table, including that the virus is linked to a high-security laboratory for the study of dangerous pathogens in Wuhan.

Despite Gao’s statement, China has been unwilling to share information nor help investigators look into the origin of the virus. China has also dismissed the theory that it originated from its Wuhan lab.

However, several government agencies in the United States, including the FBI, have concluded that the lab leak theory is the “most likely” origin of the virus.

Last month, a Chinese official dismissed the FBI’s conclusion that the lab leak theory was the likely origin.

“‘A laboratory origin of the pandemic was considered to be extremely unlikely’ is a science-based, authoritative conclusion reached by the experts of the WHO-China joint mission after field trips to the lab in Wuhan and in-depth communication with researchers,” Foreign Ministry spokeswoman Mao Ning said.