The first known case of coronavirus was a vendor from China’s Wuhan animal market and not an accountant, a study published in the Science journal on Thursday said.

The origin of the coronavirus, which is yet to be determined, had caused tensions between the United States and China since the pandemic began last year. There have been theories that the virus emanated from a lab in Wuhan.

Several experts, including Peter Dazak who was on the World Health Organization coronavirus investigation team, were convinced by the study conducted by Michael Worboy, AFP reported on Thursday.

“In this city of 11 million people, half of the early cases are linked to a place that’s the size of a soccer field,” said Worobey, according to The New York Times. “It becomes very difficult to explain that pattern if the outbreak did not start at the market.”

Worobey added that the accountant, who was considered to be the first coronavirus patient, was not ill on December 8.

“Fever and other coronavirus symptoms [in the accountant] started on December 16 after multiple workers at the Hunan market were already exhibiting signs of infections, including the seafood vendor whose symptoms began December 11,” Woroby’s study said.

However, some experts also said that the evidence was insufficient to determine the beginning of the coronavirus pandemic, according to The New York Times.

“I don’t disagree with the analysis,” said Jesse Bloom, a virologist at the Fred Hutchinson Cancer Research Center. “But I don’t agree that any of the data is strong enough or complete enough to say anything very confidently, other than that the Huanan Seafood Market was clearly a super-spreading event.”