DeKalb County police and school district officials are investigating the discovery of a weapon found Thursday in an adult restroom inside Kingsley Elementary School.

The Dunwoody school went on lockdown for about 30 minutes. No one was harmed or injured, the school’s principal, Tyra Harris-Thompson, said in a letter.

The letter did not specify the type of weapon but said it belonged to a school employee, who was not identified. District officials said Friday the employee has been placed on paid administrative leave until the investigation is completed.

“Please know that we will continue to do everything we can to ensure the safety of our students and staff,” the principal wrote. “This incident is another reminder of the DeKalb County School District’s ‘See Something, Say Something’ campaign that encourages anyone who suspects any unsafe situation on campus to report it promptly to school staff or law enforcement.”

District officials said they would decline additional comment to avoid compromising the integrity of the ongoing investigation.