WUHAN, Nov. 28 (Xinhua) -- The city of Wuhan in central China has found that three imported frozen food packaging samples tested positive for the novel coronavirus, the municipal health commission said on Saturday.

According to the commission, two samples were taken from frozen beef from Brazil in a refrigerated warehouse and the other one from frozen basa fish from Vietnam in another warehouse.

Local authorities have sealed the products, quarantined, and conducted nucleic acid tests on relevant personnel who had direct contact with the food. So far, all results showed negative.

The shipments of frozen food from which the tainted samples were taken had not been released to the market.

China has increased efforts to block COVID-19 through imported foods, with the Ministry of Transport releasing a guideline in mid-November to prevent the transmission of COVID-19 through imported cold-chain foods in road and water transportation.

The State Council joint prevention and control mechanism against COVID-19 has also unveiled a plan to realize full-chain, closed-loop, traceable management of imported cold-chain foods.