All environmental and key raw food samples collected from local wet markets have so far tested negative for coronavirus, the Shanghai Center for Disease Control and Prevention said on Tuesday.

Early cases of COVID-19 in Wuhan were traced to the city's Huanan seafood market, and the recent coronavirus outbreak in Beijing has also been linked to itsXinfadi wholesale food market. In response, city- and district-level disease control centers in Shanghai have started collecting and testing samples from local wholesale markets, wet markets and large supermarkets this month.

Major targets of inspection include areas of food processing, water samples, frozen aquatic products and meats.

By Tuesday, a total of 5,681 samples from some 300 markets across all 16 districts have been collected and the results so far were all negative for the virus. Some samples were still underoging examination, disease control authorities say.

Monitoring will continue at local markets and continued testing will be conducted, officials say.

A disease control official collects a sample from a meat stall.

An official collects samples from a meat processing machine.