Dr. Anthony Fauci, the nation’s top infectious disease expert, once again found himself embroiled in a heated back-and-forth with Sen. Rand Paul (R-KY) during a Tuesday Senate coronavirus hearing, this time over accusations that he funded a Wuhan lab to develop COVID-19.

Paul, who signaled on Monday that he was going to grill Fauci on the subject, alleged that gain-of-function research to mutate animal viruses to infect humans at the Wuhan Institute of Virology had been funded by the National Institutes of Health, something that Fauci strongly disputed. “With all due respect, you are entirely and completely incorrect that the NIH has not ever and does not now fund gain-of-function research in the Wuhan institute,” Biden’s chief medical advisor said.

Paul, however, continued to suggest Fauci was personally involved in bioengineering and weaponizing COVID-19, prompting an exasperated Fauci to push back. “I do not favor gain-of-function research in China. That is not correct,” he said, eventually adding: “You are saying things that are not correct!”