The head of the World Health Organization (WHO) said further investigation was needed to conclusively rule out that Covid-19 emerged from a laboratory in China.
Tedros Adhanom Ghebreyesus said that while a lab leak was the least likely cause, more research was needed.
The United States and other countries have criticized China for not providing the WHO with sufficient data.
Beijing has consistently rejected the virus leak allegations.
A WHO and Chinese expert report released on Tuesday said the explanation for the lab leak was highly unlikely and the virus likely passed from bats to humans via another animal intermediary.
China has yet to respond to the latest WHO statement.
‘All the assumptions on the table’
However, the theory that the virus could have come from a leak in a lab “requires further investigation, potentially with additional assignments involving specialist experts,” Dr Tedros said on Tuesday.
“Let me make it clear that when it comes to the WHO, all assumptions remain on the table,” he added.
The virus was first detected in Wuhan, China’s Hubei province at the end of 2019. An international team of experts visited 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.
The team investigated all possibilities, including a theory that the virus originated from the Wuhan Institute of Virology. The institute is the world’s leading authority on the collection, storage and study of bat coronaviruses.
In response to the WHO report, the United States and 13 allies, including South Korea, Australia and the United Kingdom, expressed concern over the results and urged China to provide “full access “to the experts.
The statement said the Wuhan mission was “significantly delayed and did not have access to original and complete data and samples.”
“Science missions like these should be able to do their job under conditions that produce independent and objective recommendations and conclusions.”
The group is committed to working with WHO.
Former US President Donald Trump was among those supporting the theory that the virus could have escaped from a laboratory.
WHO investigative team leader Peter Ben Embarek said on Tuesday his team had felt under political pressure, including from outside China, but said he did not ‘had never been in a rush to take anything out of the team’s final report.
He also confirmed that his team had found no evidence that Wuhan labs were involved in the outbreak.
Dr Embarak also said it was “perfectly possible” for cases to circulate in the Wuhan area in October or November 2019. China informed WHO of the cases on January 3, a month after the first reported infection.
China has always refuted claims that the virus originated from a laboratory and claims that although Wuhan is where the first cluster of cases were detected, this is not necessarily the origin of the virus.
State media claimed that the virus may have arrived in Wuhan during frozen food imports.
The country has largely brought its own outbreak under control thanks to rapid mass testing, strict lockdowns and strict travel restrictions.
Globally, more than 127 million people have contracted the virus since it was first identified, and more than 2.7 million people are known to have died from it.