Subsequent research found earlier cases among people not linked to the market, undermining that theory. Investigators looked further and found “important clues” about the market’s role, Daszak said, declining to elaborate.

“Right now, we’re trying to tease everything together,” he said. “We’ve looked at these three strands separately. Now we’re going to bring it together and see what everything tells us.”

While the food market was shuttered and cleaned almost immediately after cases were recognized, “it’s still pretty intact,” Daszak said. “People left in a hurry and they left equipment, they left utensils, they left evidence of what was going on, and that’s what we looked at.”

Scientists in China who took environmental samples inside the market identified sites where traces of SARS-CoV-2 were detected, he said. Investigators also benefited from greater understanding of Covid-19.