The head of the World Health Organization (WHO) has said further investigation is needed to conclusively rule out that Covid-19 emerged from a laboratory in China.
Tedros Adhanom Ghebreyesus said that although a lab leak was the least likely cause, more research was needed.
The US and other countries have criticised China for failing to provide the WHO with sufficient data. Beijing has always dismissed the allegations of a virus leak.
A report by WHO and Chinese experts released on Tuesday, said the lab leak explanation was highly unlikely and the virus had probably jumped from bats to humans via another intermediary animal.
However the theory that the virus might have come from a leak in a laboratory “requires further investigation, potential with additional missions involving specialist experts,” Dr Tedros said on Tuesday.
“Let me say clearly that as far as WHO is concerned, all hypothesis remain on the table,” he added.
The virus was first detected in Wuhan, in China’s Hubei province in late 2019. An international team of experts travelled to to the city in January to probe the origins of the virus.
Their research relied on samples and evidence provided by Chinese officials but Dr Tedros said the team had difficulty accessing raw data and called for “more timely and comprehensive data sharing” in the future.
Worldwide, more than 127 million people have caught the virus since it was first identified, and more than 2.7 million people are known to have died from it.