President Biden said Wednesday he had asked U.S. intelligence agencies to “redouble their efforts” to determine the origin of the coronavirus, an abrupt departure from the previous White House position of relying on the World Health Organization to uncover how the contagion started.

The new message reflects a notable shift in some prominent scientists’ assessments that the virus all but certainly jumped from an animal species to humans. The theory that has more recently gained traction is that the pandemic — which has killed more than 3.4 million people worldwide — may have accidentally escaped from the Wuhan Institute of Virology in China, though that is far from conclusive. Biden ordered intelligence officials to deliver a report within 90 days “that could bring us closer to a definitive conclusion.”

Some Republicans pushed the idea early on that the Wuhan lab, rather than a natural transmission from animals to humans, was at fault. Among them was former president Donald Trump, who often used inflammatory language to describe the virus’s origins in China.

But that notion was dismissed by Democrats and many scientists, who viewed the focus on the lab as part of a larger attack on China that fueled an increase in hate crimes against Asian Americans.

“There was so much inaccurate information flowing from the White House that many viewed this as just another thing that was not true and a way for the White House to divert attention from a fledgling covid response,” said Chris Meekins, a former Health and Human Services official who is now an analyst at Raymond James, a financial services firm.

But in recent weeks, some notable researchers have begun arguing more pointedly that the lab theory should remain on the table until more is known, including some who made the case in an article in the journal Science. A series of reports in the Wall Street Journal, including one highlighting how several Wuhan lab employees became sick in fall 2019 with covid-like symptoms, have boosted the reexamination.

The origin of the deadliest pandemic in recent memory carries enormous implications for public health — and beyond. If investigators point to China, one of the most powerful and sensitive countries in the world, it could ignite a global diplomatic firestorm.

Health officials complain that China has hampered investigations into the matter, and a definitive finding could remain elusive despite Biden’s directive. But Wednesday’s movesuggests he is growing more concerned about China’s possible role.

Some scientists cautioned that despite the renewed interest, no significant new information has emerged in recent weeks. They urged Biden to ensure that intelligence officials provide clear evidence in their upcoming report, which they are typically reluctant to do.

“The only way this will be useful is if Biden can get some concrete information on the supposed infections in Wuhan Institute of Virology lab workers in fall 2019,” said Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan.

She cautioned that the mere fact that several people from the lab were ill shortly before the outbreak is hardly proof. “There’s nothing remarkable about three people seeking medical care during cold [and] flu season in a city of 11 million people,” Rasmussen added. “It’s not proof they had covid.”

The White House shift also signals less deference to the WHO, which Biden had been seeking to bolster as part of his effort to restore global institutions after the Trump administration. Biden made rejoining the WHO one of his first moves as president.

As recently as Tuesday, the Biden administration had stressed that the WHO should lead efforts to uncover the cause. Biden “believes there needs to be an independent investigation, one that’s run by the international community,” White House press secretary Jen Psaki said Tuesday.

But the WHO has struggled in the past to reach a definitive conclusion on the origin of the virus, partly due to what officials say is China’s unwillingness to cooperate with investigators.

After Biden’s announcement, White House spokeswoman Karine Jean-Pierre declined to give a specific reason for the shift. “This is just a continuation of what the president has been focused on,” she said.

The president’s statement did provide an unusual window into a debate within U.S. intelligence agencies on the virus’s origins.

Biden disclosed that he asked for an initial review in March, and that “one element” of the intelligence community “leans” toward the view that the novel coronavirus came from a laboratory accident. Two other components, he said, believe the virus came from animal-to-human contact.

A person familiar with the White House deliberations, who spoke on the condition of anonymity to discuss the talks, said Biden had not been satisfied with the initial report that he’d assigned in March, adding, “It was clear to all we could and must do more beyond existing efforts.”

Wednesday’s announcement “took some time to declassify,” the person said, acknowledging that it’s “a very rare step” to reveal debate within the intelligence community.

Biden’s statement disclosing that internal split may have been a way to signal his displeasure with the initial report. “It is very unusual for a president to issue such a public statement, which some would consider a not-so-mild rebuke of the intelligence community’s work,” said a former senior intelligence officer, who spoke on the condition of anonymity to candidly describe the president’s remarks.

The person familiar with the White House deliberations also noted that China had “made clear” at a WHO meeting Tuesday that it “had no intention” of participating in the next steps of the investigation. That “ignited heightened interest to take additional steps from the United States to investigate the origins using the resources of our intelligence team and our health experts,” the person said.

Current and former intelligence officials who favor the lab leak hypothesis have pointed to what they see as two pieces of what they call compelling evidence in the intelligence that has been gathered so far.

The first is that staff members at the Wuhan Institute of Virology became sick in the fall of 2019 with symptoms that resembled covid-19, the disease caused by the coronavirus, as well as seasonal illnesses. David Asher, a former State Department official who led the department’s investigation into the pandemic’s origins, described the sick lab workers as “the first known cluster that we’re aware of, of victims of [what] we believe to be covid-19.”

Asher added, “There is a possibility it was influenza, but I’m very doubtful that three people in highly protected circumstances in a level-three laboratory working on coronaviruses would all get sick with influenza that put them in a hospital or in severe conditions all in the same week, and it didn’t have anything with the coronavirus. That’s highly hard to believe.”

A second piece of evidence is the Chinese military’s alleged involvement in bioweapons programs and its connection to the Wuhan lab. Those who suspect the lab say that helps explain the Chinese government’s refusal to allow close inspection of the lab and its records.

Trump has seized on the developments to contend he was right all along in blaming China and that his critics have been proved wrong. Biden sought to frame the matter differently, suggesting it was Trump’s negligence in the first place that cost the United States the opportunity to know more.

“Back in early 2020, when covid-19 emerged, I called for the [Centers for Disease Control and Prevention] to get access to China to learn about the virus so we could fight it more effectively,” Biden said. “The failure to get our inspectors on the ground in those early months will always hamper any investigation into the origin of covid-19.”

In early 2020, Trump praised China repeatedly for its handling of the virus. “China has been working very hard to contain the Coronavirus,” he tweeted in January 2020. “The United States greatly appreciates their efforts and transparency.”

Soon afterward, however, Trump reversed course and threatened to pull the United States out of the WHO and accused the organization of being too deferential to China. He made official moves to do so in July 2020.

Other Democrats also took a tougher tone Wednesday. Rep. Diana DeGette (D-Colo.) agreed that the lab theory should be investigated. “It’s very important that we find — that we investigate particularly if the virus escaped from some lab,” she said.

Some Republicans, meanwhile, are suggesting that their early suspicions of the Wuhan lab were dismissed prematurely.

“The common-sense case for a lab leak is the same as it was in January 2020, when I first mentioned the possibility,” Sen. Tom Cotton (R-Ark.) tweeted this week. “The United States & the world must demand a full, impartial investigation into COVID-19 origins, with a special focus on the Wuhan labs.”

But when the debate first heated up in early 2020, discussions of the lab were often conflated with conspiracy theories and unsupported claims that China had deliberately engineered the virus to harm the United States.

Scott Gottlieb, who headed the Food and Drug Administration under Trump, said it is crucial to distinguish between the conspiracy theories involving sinister plots and legitimate questions about the lab’s procedures.

“We can’t let the more politically fanciful narrative obscure the more likely but equally epochal reality that this could have been the result of tragically poor lab practices,” Gottlieb said.

The debate has now flared up again in Congress, with Sen. Rand Paul (R-Ky.) and other Republicans criticizing a subcontract that the Wuhan Institute received under a grant from the National Institutes of Health. The Senate on Tuesday approved Paul’s proposal to permanently ban all funding of “gain-of-function” research, which can involve enhancing a virus’s strength, in China.

NIH Director Francis Collins has repeatedly said the Wuhan lab was not authorized under the NIH grant to conduct that research.

Meanwhile, Trump has been trying to frame the fresh examination of the lab theory as a victory.

In an interview with Newsmax on Tuesday night, Trump stressed his early suspicions that the lab was the source of the virus. “I said right at the beginning that’s where it came from,” Trump said. “It was obvious to smart people that’s where it came from. I have no doubt about it.”

John Wagner contributed to this report.