Dr. Anthony Fauci, the top U.S. infectious disease expert until leaving the government in 2022, faced heated questioning Monday from Republican lawmakers about the origins of the COVID-19 pandemic.

A Republican-led subcommittee has spent over a year probing the nation’s response to the pandemic and whether U.S.-funded research in China may have played any role in how it started. Democrats opened the hearing saying the investigation so far has found no evidence that Fauci did anything wrong while missing an important opportunity to prepare for the next scary outbreak.

Fauci – alternately a trusted voice during the pandemic and the target of partisan attacks, even death threats – spent 14 hours over two days in January being grilled by the House panel behind closed doors. On Monday, they questioned him again, in public and on camera for the first time since he ended more than five decades of government service.

This time around he faced a new set of questions about the credibility of his former agency, the National Institutes of Health. Last month, the House panel revealed emails from an NIH colleague about ways to evade public records laws, including by not discussing controversial issues on government email.