Shulan in Jilin province, has raised its COVID-19 emergency level after a cluster of 12 cases were reported, the provincial epidemic prevention and control office said on Sunday.
The Health Commission of Jilin Province reported 11 new, locally transmitted, confirmed cases in Shulan on Sunday.
The province's COVID-19 epidemic control team categorized Shulan on Sunday as a high-risk epidemic region, the only one in the country.
On Thursday, a 45-year-old woman was diagnosed with COVID-19. The city upgraded its emergency response from low-level to medium risk.
Jilin had gone without new cases for 73 days.
The 11 new cases include the woman's relatives and people who had close contact with them.
She reportedly had not left the province and had no contact elsewhere. Further investigation is underway to find the source of her infection.
"After months of effort, the overall situation across the province is stabilizing," Bayin Chaolu, Party secretary of Jilin province, said in a videoconference in Jilin City on Sunday. "However, the cluster infections have appeared in Shulan, reflecting obvious weaknesses and problems in our epidemic prevention and control work."
He pointed out that related departments and officials must be held accountable for the epidemiological investigation of all confirmed cases, suspected cases, asymptomatic cases and their close contacts, in an effort to isolate the source of infection.
A total of 254 related close contacts have been placed in quarantine, the provincial health commission said.
All residential communities and villages in Shulan have been locked down since Saturday morning, the local epidemic control department said.
Families are allowed to send one member outside each day to make purchases. Residents must register information and scan health codes when entering and leaving their communities, and masks and temperature checks are mandatory. Visitors are not allowed.
All public service and entertainment facilities have been suspended and restaurants have stopped dining room services.
Residents are urged to avoid gathering in public areas.
China Railway Shenyang Group temporarily canceled train service between Shulan and some cities, including Changchun, starting on Sunday.
Neighboring Heilongjiang province reported a new confirmed case on Sunday involving a 70-year-old man who was a close contact of a person infected in Harbin. The elderly man has received treatment in quarantine for rectal cancer and high blood pressure at the First Affiliated Hospital of Harbin Medical University since April 9.
He tested negative for the virus seven times before being diagnosed with COVID-19 on Saturday.
Also, a 23-year-old man who arrived at Shenyang, Liaoning province, from Jilin City on Tuesday was hospitalized on Friday and diagnosed with COVID-19 on Sunday.