TIANJIN, Nov. 8 (Xinhua) -- A cold storage worker in north China's Tianjin Municipality tested positive for COVID-19 and has been sent to a designated hospital for treatment, the local health authority said Sunday.

An environmental sample from a doorknob at Hailian Cold Storage, located in Binhai New Area, was also found positive for the coronavirus, said the municipal epidemic prevention and control headquarters, adding that other workers, as well as vicinities of the cold storage facility, tested negative.

Nucleic acid tests are being conducted on close contacts of the worker and more environmental samples, while an investigation to trace the virus source is also underway as part of anti-epidemic efforts, according to the authorities.

On Saturday, Tianjin received reports from the cities of Dezhou in Shandong Province and Taiyuan in Shanxi Province, on the detection of novel coronavirus on the outer packaging of imported frozen food transported via Tianjin.

Tianjin immediately launched an emergency response, conducting tests on frozen food, cold storages, and transport vehicles as well as on workers and their close contacts related to the cold storage facility.

The cold storages have been closed. Relevant provinces and cities have been alerted against the cold-chain food from Tianjin's cold storages.