York High School was locked down Thursday morning after a report that a student had a gun.

Police took a student into custody and discovered that the gun was a knife but might have appeared to be a firearm when it was in its sheath, said a press release from York police.

The incident began on a school bus where a middle school student saw a high school student with what appeared to be a gun, police said. When the middle school student arrived at school he alerted the school resource officer.

The high school was placed in lockdown and five officers, two of them school resource officers, responded, police said. The student was located in the class the student was scheduled to be in and taken into custody, at which point authorities discovered the weapon was a knife, police said.