Garden City High School is on non-emergency lockdown while police and district officials investigate why a bullet casing was left on a hallway floor.
Brian Sumner, associate superintendent of Garden City Public Schools, said no students are in danger and the lockdown is being done as a precaution.
"We're following our protocols for lockdowns and law enforcement is on site," he said. "No one's safety is in jeopardy. There's nobody suspicious on site."
He said no shots were fired and no one was injured.
Sumner also said the district will release a statement after officials finish their investigation.