Shanghai will launch another round of slice-and-grid screening starting Saturday with combined methods of antigen and nucleic testing, the municipal health commission announced on Saturday.

Wu Jinglei, director of the municipal health commission, said community control and nucleic acid testing will be conducted in high-risk areas for COVID-19 exposure.

The rapid COVID-19 antigen test kits will be distributed to households in low-risk areas and if the result of any self-test returns positive, the person involved should report to local community workers and stay in place for a follow-up nucleic acid test, he said.

Shanghai reported 38 locally transmitted COVID-19 cases and 2,231 local asymptomatic cases on Friday, according to the commission.

"The high number of the infections was partly due to a few days' delay in producing results from previous grid testing," explained Wu Fan, member of the expert team leading the Shanghai COVID-19 prevention and control efforts. Wu said it is vital that the combined testing program covers the entire city.

"We ask for the our citizens' cooperation; that they refrain from going out before they get their negative test result," she said. "We will give priority to essential workers in our testing so the city can keep running."

Hospitals are required to adopt scientific and reasonable control measures by setting up green lanes and quarantine wards for patients with critical illnesses, making sure that everyone involved receives timely treatment, director Wu Jinglei said.

"Top-class comprehensive hospitals, emergency departments in children's hospitals and fever clinics must fully prepare for their staff protection and facilities to ensure their medical services are uninterrupted," he added.

Facing a surge in COVID-19 patients, Shanghai has converted and opened seven reserve quarantine facilities, including two stadiums in Minhang and Jiading.

The city will also open the Shanghai World Expo Exhibition and Convention Center to receive asymptomatic cases and mild cases on Saturday.