Scientists searching for the origins of COVID-19 have zeroed in on a short list of animals that possibly helped spread it to people, an effort they hope could allow them to trace the outbreak back to its source.

After an in-depth analysis of the genetic material from hundreds of swabs taken from the walls, floors, machines and drains inside the Huanan Seafood Wholesale Market in Wuhan, China — a site that’s been described as an epicenter of early spread of Covid-19 — scientists say they now know exactly which species of animals were in the same area where investigators also found the most positive samples the virus that causes Covid-19.

Genetic evidence from a new report suggests the coronavirus pandemic most likely spilled over from animals in the Wuhan market.