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Sen. Tom Cotton said on Friday that China’s cover-up of the origin of the coronavirus outbreak may have been the “deadliest and costliest” move in human history.

“The circumstantial evidence, which I began to cite in January, is stacking up pretty quickly that this virus may have originated in those labs in Wuhan, China,” the Republican Arkansas lawmaker told “Fox & Friends.”

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U.S. officials are increasingly confident the virus likely escaped from a lab in Wuhan, China, where it was being studied.

Cotton said that it was known from the very beginning that the Chinese Communist Party’s “front story” about the coronavirus originating in [wet] food markets within China “was probably wrong.”

“For one, it appears that they don’t even sell the kind of bats at that market from which this virus originated,” Cotton said.

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Multiple sources who have been briefed on the details of early actions by China's government and seen relevant materials tell Fox News that the virus – a naturally occurring strain that was being studied at the Wuhan lab – was initially transmitted from a bat to a human. It is believed that "patient zero" worked at the Wuhan lab.

Cotton also said that China is known for having a “sloppy history of laboratory safety.”

“Some of our own diplomats at the embassies in China went to these labs as far back as two years ago and said that the practices there were very alarming," Cotton said.

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“You can see how the Chinese Communist Party has continued to lie about this from the very beginning as if they have something to cover up,” Cotton said.

“If that’s the case, it really is the biggest, the costliest, the most deadly cover-up in the history of mankind,” Cotton concluded.

The “increasing confidence” comes from classified and open-source documents and evidence, the sources said. Fox News has requested to see the evidence directly.

Sources emphasized – as is often the case with intelligence – that this version of events is not definitive and should not be characterized as such. Some inside the administration and the intelligence and epidemiological communities are more skeptical, and the investigation is continuing.

Fox News' Brett Baier and Gregg Re contributed to this report.