In an article published Sunday, the WSJ writes that the U.S. Energy Department has recently updated its assessment of how the novel coronavirus behind the pandemic emerged: While the department previously said it was undecided on the matter, it now calls the lab-leak theory the most likely explanation.

The department shared its updated assessment, which it noted it has low confidence in, in a classified intelligence report provided to the White House and key lawmakers, according to the Journal, which cited people who have read the report.

The department joins the FBI in backing the lab-leak theory, while four other agencies and a national intelligence panel believe the virus emerged through natural transmission, and two are undecided, the Journal wrote.

The pandemic’s origin has been hotly debated for years. The coronavirus was circulating in Wuhan, China, in late 2019. The city was known to have an array of labs—including the Wuhan Institute of Virology, the Chinese Center for Disease Control and Prevention, and the Wuhan Institute of Biological Products—and was considered the center of China’s coronavirus research, with many of its labs expanded or built after the SARS epidemic in the early 2000s.

On the other hand, the city, like many others in China, was home to numerous wet markets, where animals are sold and slaughtered. Many scientists favor the theory that the virus emerged from such a market.

In July of last year, two extensive, peer-reviewed papers in Science from an international team of scientists concluded that the coronavirus most likely jumped from a caged wild animal into people at the city’s Huanan Seafood Wholesale Market. Other scientists not involved in that study considered it a blow to the lab-leak theory.

“The studies don’t exclude other hypotheses entirely. But they absolutely are pushing it toward an animal origin,” virologist Jeremy Kamil, at Louisiana State University Health Shreveport, told NPR at the time. 

Adding to the lab-leak theory was U.S. intelligence that several Wuhan Institute of Virology researchers sought hospital care in November 2019, the Journal noted, though a House Intelligence Committee report published in mid-December last year noted those individuals might have simply had a seasonal flu.

Republican lawmakers who took control of the House last month are pursuing investigations into pandemic’s origins, as are their Senate counterparts, fulfilling pledges made on the campaign trail last year.