BEIJING, -- Through extensive testing of animal products at the Huanan seafood market in Wuhan, none of the animal products sampled in the market tested positive, said a senior expert on March 31.

Environmental samples taken after the seafood market was closed revealed widespread environmental contamination by the virus, particularly in the aquatic products stalls, said Liang Wannian, team leader of the Chinese side of the WHO-China joint team studying the COVID-19 origins.

The findings suggest that the market had the possibility of introducing the virus through infected people, contaminated cold-chain products, animals and animal products, Liang noted.

"We have yet to carry out relevant tests on cold chain products," he added.

Liang made the remarks at a press briefing by the Chinese members of the WHO-convened global study of the origins of the virus on Wednesday in Beijing.