At least 21 people, including 19 students, have tested positive for COVID-19, after attending an outdoor graduation ceremony and prom in Missouri earlier this month, according to school officials on Monday.

St. Dominic High School in O’Fallon, a suburb northwest of St Louis, hosted the ceremony on July 8, and prom was held on July 10. The school was later notified that 19 students and two guests tested positive for the virus.  All of those who were infected experienced symptoms.

“Upon learning of the first positive case, we informed all families with students who attended either event, and have encouraged them to follow the guidance recommended by local health officials and the CDC, including monitoring their children for any symptoms of COVID-19,” according to a news release by the school.

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The school said it was canceling all student activities through Aug. 9, so families could take the necessary precautions before the start of the academic school year, which is set to begin on Aug. 10. Classes start a week later -- on Aug. 17.

“We will continue to monitor the situation, and will determine any further measures that need to be taken,” the release said.

The graduation ceremony was held outdoors, while the prom was held at an "offsite" venue, the school said. St. Dominic President Jim Welby tweeted photos of the outdoor graduation venue, which showed rows of white chairs in the school's football stadium.

Meanwhile, the school's Facebook Live broadcast of the graduation ceremony has since been removed, according to St. Louis' KSDK.

Missouri Gov. Mike Parson said during an interview with St. Louis radio host Marc Cox Friday that he is pushing for schools to reopen this fall, even though he acknowledged most students will likely contract the virus.

“These kids gotta get back to school,” Parson said. “They’re at the lowest risk possible and if they do get COVID-19 -- which they will, and they will when they go to school -- they’re not going to the hospitals, they’re not going to have to sit in doctors’ offices."

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He continued: "They’re going to go home, and they’re gonna get over it, and most of it all proves out to be that way if you look at the science of it," according to the Kansas City Star.

The coronavirus has killed more than 140,000 people in the U.S. since the start of the pandemic, with 31 of those deaths involving children under the age of 15, according to a July 15 Centers for Disease Control and Prevention report. Meanwhile, at least 157 people have died between the ages of 15 to 24.

“At this time, we are focusing on communicating with our school community, as well as on working with local health officials and the Archdiocese of St. Louis to ensure all guidelines and protocols are followed," the school added on Monday. "As we continue to plan for the school year, we are keeping the physical, spiritual, intellectual and emotional health of our students at the forefront."

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Details involving the return to St. Dominic High School will be shared with families next week.