Companies in Shenzhen, a major Chinese business center, will be allowed to reopen while efforts to contain coronavirus outbreaks progress, the government said Thursday, following a citywide shutdown that rattled financial markets.

Testing of everyone in the city of 17.5 million people is “progressing smoothly,” said a deputy mayor, Huang Qiang, at a news conference. He said 71 new cases were found in the 24 hours through midnight Wednesday.

China’s case numbers in its latest wave of outbreaks in areas throughout the country are relatively low. But authorities are enforcing a “zero tolerance” strategy that has temporarily shut down major cities to find isolate every infected person.

“We will organize enterprises to return to work,” Huang said, according to a transcript released by the government. He gave no timetable but said businesses are required to step up strengthen anti-disease measures and monitor employees for the virus’s telltale fever.

Chinese leaders appear to be trying to fine-tune their disease-control system to maintain their goal of zero cases while reducing economic and social disruption from stringent controls.

A meeting Thursday of leaders of the ruling Communist Party “stressed the need to maintain normal production” but said disease control work should be “carried out strictly,” state TV reported on its evening news.

“We should accelerate the reform of the disease control system,” the party leaders were cited as saying at the meeting. The report gave no details of possible changes under consideration.

Businesses in Shenzhen, a finance and technology hub, were ordered to close Monday, except those that supply food, fuel and other necessities. Bus and subway service shut down. Residents were told to stay home while authorities carried out three rounds of testing.

That prompted alarm about the possible impact on smartphone manufacturing and other industries that are centered on Shenzhen, which abuts Hong Kong. Economists said a potential threat to trade loomed if anti-virus controls spread to Shenzhen’s Yantian Port, one of the world’s business.

Elsewhere, the industrial center of Changchun in the northeast shut down and travel controls were imposed on its surrounding province of Jilin.

Volkswagen AG said production at its factory in Changchun would remain idle Friday. The German automaker said a factory in Shanghai, where anti-disease controls also were tightened, would operate.

Shenzhen is home to some of China's biggest companies including telecom equipment maker Huawei Technologies Ltd., Ping An Insurance Co. of China, electric vehicle maker BYD Auto and Tencent Holding, operator of the popular WeChat message system.

In Shenzhen, the "epidemic prevention and control situation is positive,” Huang said.

However, Huang warned Shenzhen still was suffering “sporadic outbreaks.” He said 71 confirmed infections were found in the 24 hours through midnight Wednesday.

“Epidemic prevention and control work cannot slacken at all,” Huang said.

- by Joe McDonald, AP