Beijing has never fully co-operated with international investigators, impeding the search for a definitive answer. But scientists continue their quest to establish the causes of a global health crisis that killed millions of people, caused trillions of dollars of economic damage and increased fears over the risks of virus research.

The nuanced finding suggests the agency believes the totality of evidence makes a lab origin more likely than a natural origin.

The problem for the lab-leak position is that the U.S. has never had access to the Wuhan lab and has thus been unable to reach a definitive answer for more than five years. Now that the CIA has at last come to a conclusion, not all scientists are sold on what it has reported, seeing the results as thinly scientifically sourced.

The Central Intelligence Agency on Saturday said it has shifted its previous assessments and has concluded that it’s likely the Covid-19 virus was leaked from a Chinese lab before it became a global pandemic but added that the agency had “low confidence” in its judgment.

China on Monday dismissed the possibility that the virus that caused COVID-19 leaked from a lab, after the CIA said it now favors the so-called lab leak theory over natural transmission. “It

The CIA now assesses the virus that causes Covid-19 more likely originated from an accidental lab leak in China, rather than occurring naturally, according to a statement from the agency Saturday, just days after Director John Ratcliffe took the reins.

The intelligence agency says it has a “low confidence” in its new finding, but this is further than it has ever gone in pinpointing the origin of a virus that killed millions worldwide.

A new analysis that began under the Biden administration is released by the C.I.A.’s new director, John Ratcliffe, who wants the agency to get “off the sidelines” in the debate.