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Rep. Michael McCaul, R-Texas, asserted Thursday that the Chinese Communist Party (CCP) engaged in the "worst coverup in human history" by failing to adequately inform and protect their own people and the world from the coronavirus pandemic outbreak.

McCaul, the top Republican on the House Foreign Affairs Committee, told "America's Newsroom" that the panel's investigation had helped reveal the chain of events surrounding the origin of the virus.

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"We know when this virus first appeared December 1st -- actually back to mid-November -- that the Chinese Communist Party went in and detained eight of the doctors who were sounding the alarm that we had a different kind of virus here that was more lethal," he recounted. "They detained those doctors and got retractions from them. After that point in time, they went into the laboratory and they destroyed lab samples in an attempt to cover up and also control the investigation.

"Then, you go into the January timeframe [and] it becomes very interesting because at that time," McCaul continued, "you have not only doctors but Taiwan and the medical personnel in Wuhan warning the WHO [World Health Organization] , and now -- we just found out -- an internal Communist Party memo, from within, in January, at very high levels warning that this was in fact human-to-human transmission."

"Why is that so important?" he asked. "Because it's infectious at that point. And then, getting to the WHO, after all this evidence is before them they meet to determine if they should issue an international public health emergency. They are gridlocked and Director General Tedros is the one who cast the tiebreaker deciding not to warn the world that we have a global pandemic on our hands.

"And then, finally, there's a festival going on in China at that time called the Spring Festival. Five million people leave Wuhan, travel throughout China, and then millions of people from China travel internationally," McCaul told host Ed Henry.

"This could have been stopped. This could have been contained. But, instead, now we have a global pandemic," he concluded.

Fox News reported Wednesday evening that multiple sources who have been briefed on the details of early actions by China's government and seen relevant materials say there is increasing confidence that the COVID-19 outbreak likely originated in a Wuhan laboratory -- though not as a bioweapon but as part of China's attempt to demonstrate that its efforts to identify and combat viruses are equal to or greater than the capabilities of the United States.

The sources believe the initial transmission of the virus – a naturally occurring strain that was being studied there – was bat-to-human and that "patient zero" worked at the laboratory, then went into the population in Wuhan.

THE CORONAVIRUS OUTBREAK, STATE-BY-STATE

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 it’s 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.

All of the sources agree that the Chinese government engaged in an extensive coverup of data and information about COVID-19, with one source saying it may be the "costliest government coverup of all time."

Fox News' Bret Baier, Gregg Re, Barnini Chakraborty, and The Associated Press contributed to this report.