(NewsNation) — The FBI has assessed that a leak from a laboratory in Wuhan, China, “most likely” caused the COVID-19 pandemic, director Christopher Wray said on Tuesday.

“The FBI has for quite some time now assessed that the origins of the pandemic are most likely a potential lab incident in Wuhan,” Wray told Fox News in an interview.

“Here you are talking about a potential leak from a Chinese government-controlled lab,” he added.

Wray’s comments follow a Wall Street Journal report on Sunday that the U.S. Energy Department had assessed with low confidence the pandemic resulted from an unintended lab leak in China.

Four other agencies, along with a national intelligence panel, still judge that the pandemic was likely the result of a natural transmission, and two are undecided, the Journal reported.

China denounced Wray’s comments on Wednesday, saying it was firmly opposed to any form of “political manipulation” of the facts.

“Based on the poor track record of fraud and deception of the U.S. intelligence community, the conclusions they draw have no credibility whatsoever,” Chinese Foreign Ministry spokesperson Mao Ning told reporters in Beijing. “We urge the U.S. side to respect science and facts.”

Wray said he couldn’t share many details of the agency’s assessment because they were classified and accused the Chinese government of “doing its best to try to thwart and obfuscate” efforts by the United States and others to learn more about the pandemic’s origins.

“I will just make the observation that the Chinese government, it seems to me, has been doing its best to try to thwart and obfuscate the work here, the work that we’re doing, the work that our U.S. government and close foreign partners are doing,” Wray said to Fox News. “And that’s unfortunate for everybody.”

The virus was first identified in Wuhan in December 2019 before spreading worldwide and killing nearly 7 million people.

The lab leak theory was initially shot down in early 2020 by top prominent scientists. Health officials like former White House medical advisor Dr. Anthony Fauci maintained the theory could not be ruled out but said the evidence available wasn’t enough for him to support it.

“No one knows, not even I, 100% at this point, which is the reason why we are in favor of further investigation,” Fauci said.

Then-President Donald Trump embraced the theory in 2020 and it became a political dividing line between Democrats and Republicans.

Reuters contributed to this report.