The Central Intelligence Agency said Saturday that it’s more likely a lab leak caused the Covid-19 pandemic than an infected animal that spread the virus to people, changing the agency’s yearslong stance that it couldn’t conclude with certainty where the pandemic started.

In one of his first acts as Donald Trump’s CIA director, John Ratcliffe had the agency publish an assessment backing the once relatively fringe theory that the COVID-19 pandemic began with an accidental leak at a research lab in the Chinese city of Wuhan.

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.