It is “extremely unlikely” the novel coronavirus came from a laboratory incident in China, according to a joint mission investigating the origins of the pandemic.
Investigators believe the most likely cause of the initial outbreak was the virus jumping from an “intermediary host species” to humans.
It means future investigations will not focus on a laboratory incident as a potential cause of the outbreak.
An international team of World Health Organisation (WHO) scientists, working with experts in China, has been researching how the COVID-19 pandemic began.
The team has visited key locations in Wuhan, where the first cases were reported, and spoken to patients, first responders and Chinese scientists.
Evidence so far suggests the novel coronavirus may have jumped from animals to humans, but the team told a news conference it is not yet sure exactly which animals it came from or where this occurred.
The hosts may have been bats or pangolins – and then jumped to another animal before coming into contact with humans – but samples of viruses found in these animals were not identical to SARS-CoV-2.
Investigators should now look at studying bats outside of China to see if they carry genetically similar viruses, the WHO’s Dr Peter Ben Embarek said.
China’s National Health Commission spokesperson Professor Liang Wannian also suggested more research is needed into whether felines could have hosted the virus.
“The susceptibility of mink and cats to SARS-CoV-2 suggests there may be additional animals, such as those belonging to the feline family, who may act as reservoirs for the virus. But there is not yet enough research to know for sure,” he said.
It is also thought likely the virus could have been transmitted from frozen food, according to Dr Embarek.
He added the virus could have emerged this way through “convoluted pathways that may have taken a long time and moved it across borders”.
Investigations have continued to focus on the Huanan wet market in Wuhan, which was linked to a cluster of initial cases.
The market had been selling frozen animal products but there were also vendors selling products from domesticated wildlife.
It is still thought to be one of the first clusters of cases, but Professor Liang said transmission was also happening in other areas of Wuhan at the time.
Scientists also revealed the novel coronavirus could have been circulating in regions outside Wuhan before the first reported cases of the outbreak.
Unpublished data suggests samples of SARS-CoV-2 were found several weeks before the first reported cases in Wuhan, Professor Liang said.
However, he added there was no evidence that COVID was spreading in Wuhan before December 2019, when the first cases were reported, after officials looked at research samples, pharmaceutical sales and hospital records.
There was also no evidence of “large outbreaks” before December 2019 in Wuhan or elsewhere, Dr Embarek said.