The municipal health commission said on Saturday that 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, reports Xinhua new agency.
Local authorities have sealed the products, quarantined, and conducted nucleic acid tests on relevant personnel who came into direct contact with the food items.
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 transmission through imported foods.
The Ministry of Transport had released a guideline earlier this month to prevent the transmission of the virus 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.