An expert group from the World Health Organization (WHO) has been gathering data on the origins of COVID-19 for more than three years, Euronews reports. And the final report, prepared by 27 scientists, has been published.

Scientists still aren’t sure how the COVID-19 pandemic—the worst health emergency in a century—began.

That was the unsatisfying conclusion from an expert group charged by the WHO to investigate the pandemic’s origins in its final report.

Marietjie Venter, the group’s chair, said at a press briefing that most scientific data supports the hypothesis that the new coronavirus jumped to humans from animals.

That was also the conclusion drawn by the first WHO expert group that investigated the pandemic’s origins in 2021, when scientists concluded the virus likely spread from bats to humans, via another intermediary animal.

At the time, WHO said a lab leak was “extremely unlikely.”

Venter said that after more than three years of work, WHO’s expert group was unable to get the necessary data to evaluate whether or not COVID-19 was the result of a lab accident, despite repeated requests for hundreds of genetic sequences and more detailed biosecurity information that were made to the Chinese government.

“Therefore, this hypothesis could not be investigated or excluded,” she said. “It was deemed to be very speculative, based on political opinions and not backed up by science.”

She said that the 27-member group did not reach a consensus; one member resigned earlier this week and three others asked for their names to be removed from the report.

Venter said there was no evidence to prove that COVID-19 had been manipulated in a lab, nor was there any indication that the virus had been spreading before December 2019 anywhere outside of China.

“Until more scientific data becomes available, the origins of how SARS-CoV-2 entered human populations will remain inconclusive,” Venter said, referring to the scientific name for the COVID-19 virus.

WHO Director-General Tedros Adhanom Ghebreyesus said it was a “moral imperative” to determine how COVID began, noting that the virus killed at least 20 million people, wiped at least $10 trillion (€8.8 trillion) from the global economy and upended the lives of billions of people.

Last year, the AP found that the Chinese government froze meaningful domestic and international efforts to trace the virus’ origins in the first weeks of the outbreak in 2020 and that WHO itself may have missed early opportunities to investigate how COVID-19 began.