Sen. Rand Paul, a Kentucky Republican, announced that he formally sent a criminal referral to the Justice Department regarding Dr. Anthony Fauci, the former National Institute of Allergy and Infectious Diseases director.

Paul cited an email from February 2020 in which Fauci wrote that scientists discussed whether COVID-19 was produced through genetic engineering at the Wuhan Institute of Virology.

“This suspicion was heightened by the fact that scientists in Wuhan University are known to have been working on gain-of-function experiments to determine the molecular mechanisms associated with bat viruses adapting to human infection, and the outbreak originated in Wuhan,” he wrote in the email, which was published by RealClearNews reporter Philip Wegmann on Saturday.

“This directly contradicts everything he said in committee hearing to me, denying absolutely that they funded any gain-of-function, and it’s absolutely a lie. That’s why I sent an official criminal referral to the DOJ,” Paul wrote on Twitter in response to Wegmann’s tweet.

During congressional questioning in May, Paul pressed Fauci on gain-of-function research in Wuhan, to which Fauci responded, “I’ve never lied before Congress.”

Fauci also told Paul, who was a practicing ophthalmologist before being elected to Congress: “You don’t know what you’re talking about.”

Paul has heavily criticized Fauci before, including for receiving taxpayer funded security even in retirement.