Beijing reported 55 new COVID-19 infections, including 51 confirmed cases and four asymptomatic cases, from 3:00 p.m. Saturday to 3:00 p.m. Sunday, local health authorities said at a news conference on Sunday.

Most of the new infections were reported from areas already under monitoring and control while only a few cases were detected from mass testing, Pang Xinghuo, deputy head of the Beijing Municipal Center for Disease Prevention and Control, said at the press briefing.

"It's a critical time for Beijing to contain COVID-19," said Pan. "The spread of the virus is at its plateau."

Pan said the measures to fight the virus must be swift and constantly adjusted to the changing situation.

Two more medium-risk areas were upgraded to high-risk areas due to six accumulated cases being reported in 14 days. Beijing had seven high-risk areas and 28 medium-risk areas as of Sunday.

New temporary hospital opens

Beijing's Xiaotangshan temporary hospital on Sunday began admitting COVID-19 cases, local health authorities said. The facility is composed of nine buildings, holding 1,200 hospital beds in total.

Xiaotangshan is located about 30 kilometers north of central Beijing and was used to treat SARS patients in 2003.

Medical equipment for patient wards, lab testing, image scanning, disinfection, sewage treatment and fire safety has passed inspection, according to previous media reports.

The hospital is currently treating 12 cases, including asymptomatic and mild cases, Beijing Youth Daily reported.