China has seen a new surge in coronavirus cases, linked to a primary school in Fujian province.
Initial reports suggest the outbreak could be due to a student's father, who tested positive last week.
Authorities in Fujian have ordered that all teachers and students must be tested within a week, after more than 100 cases were reported in four days.
The latest wave comes a month after China contained the Nanjing outbreak - its biggest since Wuhan.
The city of Putian in Fujian province - home to about three million residents - appears to be among one of the hardest-hit places.
The first cases there have been linked to a primary school.
The suspected source of the outbreak is a student's father who tested positive for the virus on 10 September - 38 days after returning from Singapore on 4 August.
He had served 21 days in quarantine, during which he had taken nine nucleic acid and serologic tests, all of which were negative, said a report in the state-run Global Times newspaper.
It is not clear if the student's father was indeed infected overseas, as such a long incubation period is very unusual.
Meanwhile, officials have taken steps to try and contain the outbreak.
Schools have been closed and anyone leaving Putian must have proof of a negative Covid test within the last 48 hours.
Public venues such a cinemas, museums and libraries have been told to suspend indoor activities, and restaurants asked to limit their operating hours.
The nearby cities of Xiamen and Quanzhou have also been affected - with services like gyms and bars closed in Xiamen city.
Some 32 virus cases were identified in Xiamen on Monday, with most of them traced back to Putian. According to the Global Times, primary studies suggest the cases are that of the Delta variant.
The cases come ahead of a week-long National Day holiday on 1 October, known as Golden Week that sees millions travel across the country.
The Mid-Autumn Festival holiday, which runs for three days, is also set to begin on Sunday.
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