China on Tuesday said it has been “open and transparent” in the search for the origins of COVID-19 after questions about how the pandemic began received new attention.

Most recently, the U.S. Department of Energy assessed, with “low confidence,” that the pandemic first detected in the central Chinese city of Wuhan in late 2019 began with the leak of a coronavirus from a lab. The report hasn’t been made public.

China had “shared the most data and research results on virus tracing and made important contributions to global virus tracing research," Foreign Ministry spokesperson Mao Ning Mao told reporters at a daily briefing.

“Politicizing the issue of virus tracing will not smear China but will only damage the U.S.' own credibility,” Mao said, in response to complaints from U.S. officials and members of Congress that China has not been entirely cooperative.

Her comments came amid continuing questions about how the virus that has killed more than 6.8 million people worldwide first emerged.

Others in the U.S. intelligence community disagree with the Energy Department assessment of the lab leak, citing differing opinions within the government. “There is just not an intelligence community consensus,” John Kirby, the spokesman for the National Security Council, said Monday.

The DOE conclusion was first reported over the weekend in the Wall Street Journal, which said the classified report was based on new intelligence and noted in an update to a 2021 document. The DOE oversees a national network of labs in the U.S.

White House officials on Monday declined to confirm press reports about the assessment.

In 2021, officials released an intelligence report summary that said four members of the U.S. intelligence community believed with low confidence that the virus was first transmitted from an animal to a human, and a fifth believed with moderate confidence that the first human infection was linked to a lab.

Some independent scientists are open to the lab-leak theory, but there is more consensus around the idea that the virus originated in an animal and then made the leap to humans at a market in Wuhan. The true origin of the pandemic may never be known, experts say.

This story originally appeared in Los Angeles Times.