The northeast Chinese port city of Dalian is suffering the worst of the country's latest COVID-19 outbreak.
Around 24 new local cases a day are being detected in the city of 7.5 million people, the highest in the Asian nation, the South China Morning Post reported.
Outbreaks in more than 20 Chinese provinces are being driven by the Delta variant.
Authorities in the city moved to suspend production at the plants following an outbreak of cases.
In one instance, 20 positive cases were reported at a seafood plant, leading to all the plants in Zhuanghe being shut down.
Chinese authorities have adopted a zero tolerance policy to suppress cases as they arise by imposing limitations on movement.
While Dalian’s health officials have implemented measures aimed at discouraging travel in and out of the city unless necessary, the impact on port traffic is currently unclear.