A delegation of experts from the World Health Organization were allowed to visit the Huanan Seafood Market and Baishazhou wet market in Wuhan, China, on Sunday under heavy security. The wet market was originally thought to be where the coronavirus jumped species in 2019, sparking the global COVID-19 pandemic, though now it is largely thought that the deadly virus originated elsewhere and spread rapidly by market goers.

The W.H.O. team trying to determine the origins of the virus had been met with setbacks in visiting the market. “Very important site visits today—a wholesale market first & Huanan Seafood Market just now,” Peter Daszak, a zoologist with the U.S. group EcoHealth Alliance and a member of the WHO team, wrote in a tweet. “Very informative & critical for our joint teams to understand the epidemiology of COVID as it started to spread at the end of 2019.” The team, who are specialists in veterinary medicine, virology, food safety and epidemiology, also visited two hospitals in the area.