Three samples collected from the outer packaging of frozen seafood imported by three enterprises in Yantai, Shandong province, tested positive for the novel coronavirus, the city's leading group for COVID-19 control said on Tuesday.

The seafood was from the same shipment that had arrived at a port in Dalian, Liaoning province.

The samples were collected by the Yantai Economic and Technological Development Area from workers and frozen products on Sunday. The presence of coronavirus was confirmed the next day by the Yantai center for disease control and prevention.

A small amount of the frozen seafood had been processed for export but the bulk of it remained in freezers and was not sold.

Local authorities have sealed the items and disinfected the three enterprises and surrounding areas.

People who came in contact with the related imported frozen seafood are all under quarantine. Testing has found all negative results.