- Coronavirus pandemic
image sourceGetty Imagesimage captionA sick child in Houston, Texas, is taken to hospital after testing positive for Covid
The US intelligence community has been unable to determine the origins of Covid-19, and is split on whether it leaked from a lab or developed in nature, according to a new report.
The report issued by the office that oversees the nation's 18 spy agencies did conclusively determine that it was not developed as a biological weapon.
Experts warn that time is running out to gather evidence of its beginnings.
China's foreign minister has dismissed the report as "anti-science".
The report from the Office of the Director of National Intelligence said the intelligence community remains divided on Covid's most likely origin.
"All agencies assess that two hypotheses are plausible: natural exposure to an infected animal and a laboratory-associated incident."
According to the report, several unnamed spy agencies thought Covid emerged from "natural exposure to an animal infected with it or a close progenitor virus". But they only had "low confidence" in this conclusion.
One intelligence agency developed "moderate confidence" that the first human infection was likely due a "laboratory-associated incident" at the Wuhan Institute of Virology, which has studied coronaviruses in bats for more than a decade.
President Biden issued a statement after the report's publication, criticising China for not co-operating with the investigation.
"Critical information about the origins of this pandemic exists in the People's Republic of China, yet from the beginning, government officials in China have worked to prevent international investigators and members of the global public health community from accessing it," Mr Biden said.
"The world deserves answers, and I will not rest until we get them, "he added.
The pandemic, which has claimed nearly 4.5 million lives around the world, began in the Chinese city of Wuhan in December 2019.
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A World Health Organization (WHO) team, which visited Wuhan, concluded earlier this year that the disease most likely spilled over from an animal sold at a market.
This conclusion has been rejected by some scientists.
In May, Mr Biden asked US intelligence agencies to assess the data and produce a report that "could bring us closer to a definitive conclusion" on the origins of the virus.
media captionCovid-19 and Wuhan: Why don't we know more?
China meanwhile has been stoking baseless claims that virus originated from Fort Detrick, a military installation in the US.
Earlier this week, the WHO panel warned that it would soon be "biologically impossible" to gather evidence dating back to the virus' origin.
"The window of opportunity for conducting this crucial inquiry is closing fast," they warned, calling on researchers and governments to expedite studies.