A health worker takes a swab sample from a citizen for COVID-19 test in Qingdao, east China's Shandong Province, Oct. 12, 2020. (Xinhua/Li Ziheng)

The city of Qingdao in east China's Shandong Province inspected companies that deal with imported frozen food and conducted COVID-19 tests on workers, local authorities said Wednesday.

The move follows a worker of a local seafood company being found an asymptomatic carrier of COVID-19 on Tuesday.

So far, 48,435 workers in the industry have been sampled for nucleic acid tests, with 48,315 testing negative and the rest awaiting results, said Chen Wansheng, deputy director of the general office of the municipal government.

Qingdao on Tuesday conducted extensive inspections of refrigerated warehouses and companies that process imported cold-chain food. Those that failed to follow COVID-19 prevention and control rules were asked to suspend operations, Chen said.

As of Monday, Qingdao had disinfected 3,513 tonnes of imported frozen food. The city will add four designated warehouses for storing, sampling, and disinfecting all imported cold-chain food.

The city has also increased the frequency of regular nucleic acid tests for those in the cold-chain food processing industry working at ports and refrigerated warehouses.