DALIAN, Dec. 20 (Xinhua) -- China's northeastern port city of Dalian has strengthened cold-chain management in the wake of new COVID-19 cases reported recently, local authorities said Sunday.

The city has put cold-chain workers under centralized and standardized management, and has ordered at least one nucleic acid test per week on employees and samples from their working environment.

Dalian found four domestically transmitted asymptomatic COVID-19 cases during regular tests on cold-chain workers on Dec. 15. The city reported two confirmed and six asymptomatic COVID-19 cases from Dec. 15 to Dec. 19.

A residential compound in the city's Jinpu New Area was classified as medium-risk for COVID-19 on Saturday. So far, 813,504 people in the area have been sampled for nucleic acid tests, with 192,567 testing negative and the rest of the results yet to arrive.