US intelligence agencies said they were "divided" on how the coronavirus that causes COVID-19 first emerged, according to an unclassified report summary released on Friday.
The agencies were instructed by US President Joe Biden to report on the possible origins of the virus but could not come to a conclusion.
They agreed that the virus was not "developed as a biological weapon" and was likely not genetically engineered but remained split on other possibilities.
The agencies had two potential hypotheses: that it came from natural exposure to an infected animal or that it resulted from a laboratory incident.
Some intelligence analysts found both hypotheses equally likely while others gave weight to a specific hypothesis.
But the analysts said they would be "unable to provide a more definitive explanation for the origin of COVID-19" unless new information or evidence emerged.
The World Health Organization sent a team of international scientists to Wuhan to study the virus' origins in January for 28 days but that report was criticised for the involvement of Beijing and the lack of raw information.
WHO scientists have said they would need further study and information but that the project had stalled. They added in a recent statement that the window of opportunity was closing for further study.
Biden criticised Chinese officials for preventing access to key information about the origins of the pandemic.
"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," Biden said in a statement released on Friday.
He added that the US would continue to try to "trace the roots of this outbreak that has caused so much pain and death around the world."
There have been around 218 million confirmed positive cases of COVID-19 globally and 4.48 million deaths.