Willow Run High School was put into lockdown Wednesday morning when a student was found with some bullets.
Washtenaw School District Spokeswoman Emma Jackson said the school had a lockdown drill already scheduled for later in the day, but moved it up in light of the situation.
Jackson said high school students and staff, along with the middle school, were put through the planned safety measures and the Washtenaw County Sheriff's Department was brought in.
No weapons were found.
Investigators asid they have no reason to believe the incident had anything to do with a criminal plot and no threats were made.
"Willow Run Community Schools places a high priority on safety and takes immediate and decisive steps to maintain a safe and productive learning environment," Jackson said.