EXCLUSIVE: Emails between two top State Department officials show the intense mistrust and interagency infighting between the department’s COVID-19 investigative team and the arms control bureaucracy over the claim the virus originated in a lab in Wuhan, China.

Fox News obtained emails sent in early January between Chris Ford, the former acting undersecretary for Arms Control and International Security, and Thomas DiNanno, the former acting assistant secretary of the Bureau of Arms Control, Verification.

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Ford was pushing back against a panel of experts’ investigation launched by the department into the origins of COVID-19, and wrote that he wanted to subject the investigative team to a higher level scrutiny. In the emails, Ford claims the investigative team kept him out of the loop, made "not-exactly-confidence-inspiring arguments" about the lab-leak theory and delayed any substantive review from scientific experts.  

In a Jan. 4 email, Ford tells DiNanno and David Asher -- a contractor who established the panel -- that he was "all for demanding more transparency" of China and "delighted to press their feet to the fire for the honesty and clarity they’ve so far refused to provide."

"As to making assertions beyond asking tough questions, however – and especially with insinuating or actually alleging sinister BW [bioweapon] work or the probability of laboratory origin – we need to make sure what we say is solid and passes muster from real experts before we risk embarrassing and discrediting ourselves in public," he wrote.

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DiNanno responds that his team briefed Ford and experts several weeks prior with slides from Asher’s findings and that "I’d like to know what in those slides they find objectionable or where clarification is required and we’ll happily clarify, source and amend as necessary."

A day later, Ford wrote back, arguing that "Asher has made me very uneasy by repeatedly arguing against having intelligence analysts involved in assessing his arguments" and that the allegations need to be evaluated carefully.

"Let me be clear: the burden of proof is upon AVC [Bureau of Arms Control, Verification] here -- particularly since the entire IC [intelligence community], even after having reissued its analysis after months of accumulating additional information, still has a completely different position on the facts," he wrote. "Your bureau needs to shoulder that burden, or stand down."

"Please stop playing games and ducking responsibility," he added. "It is discreditable."

On Fox News Channel's "The Story" on Friday, Asher described Ford’s claim that he was against having intelligence analysts involves in assessing the claims as "nonsense, total nonsense."

"I can recall sending I think 26 pages of questions, I can't quite remember the exact length as it went to different intelligence agencies with specifics. I was in close partnership with our national laboratories who most definitely are more expert than anyone else in the scientific community in our country related to biological defense, and the use of gain of function in a dual use setting," he said.

The revelations come amid claims from former State Department officials that Ford and his team stonewalled the investigation and failed to investigate the claims -- amid broader concerns that it could open a "can of worms" about U.S. funding of that research.

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In an interview with Fox News last week, Asher said of Ford: "He seemed disinterested." 

"He said even if we came to it, how do we know where it came out of, what lab? I very rarely in my life in government have ever encountered someone who is more of a neg-acrat, less a bureaucrat than that individual is," he said. "I rarely say that I encountered disgraceful behavior in government, but I did actually on this occasion."

The claim that the virus may have originated in the Wuhan Institute of Virology, rather than a natural transmission from animals to humans, was promoted by a number of officials during the Trump administration, but dismissed at the time by a number of experts and many in the media.

But the theory has been gaining steam again in recent weeks, in part due to reports that a number of researchers at the laboratory were hospitalized with COVID-like symptoms in November 2019. The intelligence community has been ordered to "redouble" its efforts by President Biden to discover what caused the pandemic that wreaked havoc across the globe.

Vanity Fair first reported that officials were told not to explore the Wuhan Institute of Virology’s "gain of function" research, because it would bring what the outlet described as "unwelcome" attention of U.S. government funding into that research, and that DiNanno wrote in a January memo that staff from two bureaus "warned" leaders within his office not to investigate the origins of the virus because it risked opening "a can of worms."

Multiple former State Department officials told Fox News that the reported memo accurately describes what was happening at State at the time and that there was an effort among some officials at the department to oppose an extensive investigation into a possible lab leak.

Another source told Fox News that nonproliferation experts told investigators not to open "the can of worms."

The State Department has rejected the claim that the investigation was stonewalled, saying "no-one prevented the disclosure of accurate, properly contextualized information."

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"No effort was made at any time to suppress or withhold information from senior policymakers or the public," a spokesperson told Fox News on Thursday. "Internal disagreements were about the quality of analysis and the importance of not overstating, or bending, evidence to fit preconceived narratives."

Fox can confirm that there was a meeting on Jan. 7 to examine the lab-leak hypothesis, in which scientific experts questioned the findings, but saw other reasons to suspect a lab origin for the virus -- including that the Wuhan Institute of Virology [WIV] never reported the infection of six miners in 2012 with a SARS virus to the World Health Organization.

According to the meeting notes, one expert -- Ralph Baric -- said that if SARS-CoV-2 had come from a "strong animal reservoir," one might have expected to see "multiple introduction events," rather than a single outbreak, though he cautioned that it didn’t prove "[this] was an escape from a laboratory." 

Baric later said the WIV will never be able to escape the idea that virus originated from the lab and added that there is a strong probability it comes from a natural source. Asher, meanwhile, mentioned the use of gain-of-function research to increase lethality of viruses and that he was shocked that someone had not raised this.

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The intelligence community recently said that it does not know where COVID-19 was transmitted initially, "but has coalesced around two likely scenarios: either it emerged naturally from human contact with infected animals or it was a laboratory accident."

The State Department spokesperson on Thursday told Fox that it will "continue pushing for a stronger, multilateral evaluation of the origins of the virus in China." 

"We need the PRC to participate in a full, transparent, evidence-based international study with the needed access to get to the bottom of a virus that's taken more than 3 million lives across the globe — and, critically, to share information and lessons that will help us all prevent future catastrophic biological threats," the spokesperson said.

Fox News' John Roberts contributed to this report.