Dr. Anthony Fauci, the top U.S. infectious disease expert until leaving the government in 2022, faces 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.