Sixty-six high schools in Incheon, South Korea, that shut on May 20 over coronavirus concerns, will reopen on May 25 the country’s Education Ministry has said.

The high schools opened on Wednesday, the first day back to school since the outbreak, but closed within two hours after two Covid-19 cases were found among the student body.

Contact tracing and tests related to the cases have since been carried out.

All 972 students who had been to the infected areas have tested negative for the novel coronavirus, the ministry said, adding that health officials believe the risk of local transmission is not high enough to keep the schools closed.

South Korea’s Itaewon nightclub cluster infection, which started in early May, has reached a total of 215 cases so far, Jung Eun-kyeong, director of the South Korean Centers for Disease Control and Prevention (KCDC) said on Friday.

He said 20 new cases of the virus had been recorded, raising the national toll to 11,142.

At least 264 people have died from the virus in South Korea.