The police in a city in central China have detained the manager of a regional coronavirus testing laboratory on suspicion of “committing acts that caused the spread of the coronavirus or seriously increased the danger of spreading it”.

In a brief statement, the police in Xuchang, a city in Henan province, also said that the authorities in the nearby city of Yuzhou were investigating the man, identified only by his surname, Zhang, for “serious criminal offences,” but they did not provide more details.

The detention, announced on Wednesday, comes as China faces its largest surge in coronavirus cases since the start of the pandemic, an effort that has relied heavily on mass testing to ferret out cases. More than 20 million people across at least five Chinese cities are under lockdown as officials seek to tamp down outbreaks before the start of the Beijing Olympics in three weeks.

Guangzhou KingMed Diagnostics Group, the parent company of the testing laboratory, said in a statement on Wednesday that the employee had been working with local health departments in Yuzhou to assist with the logistics of the city’s mass-testing campaign. The company said the employee had not been involved in any of the laboratory testing.