Clayton County’s Harper, Callaway and Morrow elementary schools will return to remote learning for the remainder of the academic year after a cluster of COVID-19 cases have been reported in those districts, schools officials say.

The district reported the first cluster on Friday at Callaway and Morrow elementary, saying a “strike team” had been sent to the schools to sanitize the buildings. On Saturday, the school system reported a similar outbreak at Harper.

The district’s last day is May 25. Leaders did not say whether students or staff were impacted.

“Please be advised that the District will continue to follow the school system’s safety protocols for sanitizing the classroom(s) and other possible affected areas in the school, in addition to working in partnership with the Clayton County Health Department,” the school system said in a release.

Clayton County brought students back to class for face-to-face instruction last month, limiting the return to elementary students. It was the last district to return to physical buildings in part due to concerns that instruction could be disrupted if schools had to close because of a COVID-19 outbreak.