MAPLE PARK – After an empty 9mm bullet shell casing was found in a hallway at Kaneland High School Wednesday, students were placed on a “hold-in-place” – or soft lockdown – for 90 minutes while Kane County Sheriff’s deputies and K-9 units searched the school, officials said.

The action bullet casing was found in a hallway near the cafeteria at 12:15 p.m., D-302 Superintendent Todd Leden said.

A hold-in-place means that students and staff were free to continue classroom activities, while the bell schedule was suspended and student entrance and exits into classrooms was limited, according to an email sent to parents about the incident.

Many students in the cafeteria were moved to the auditorium while leaving their belongings in the cafeteria where dogs searched, Leden said.

As to whether students had been planning a walkout similar to those held at other high schools in protest of gun violence, Leden said no student had approached administrators about it.

“We had not had that conversation,” Leden said. “We will begin that conversation for March 14,” when a national school walkout is being planned.

After a search of the school, no threat was found, and students were released from their hold-in-place, Leden said.

“No other threat was found,” Leden said. “We took every safety precaution we could and the dog went in all the major areas and checked all the backpacks left in the cafeteria. The sheriff’s department will keep officers here through the end of the day.”

The email sent to parents stated that the safety of Kaneland students and staff is the district’s highest priority.

“Therefore, we felt it was important to take the most comprehensive steps at our disposal to ensure the safety of our building,” the email stated.

“Upon assurance from the law enforcement team at approximately 1:40 p.m. that the building was safe, we resumed an adjusted bell schedule and the hold-in-place was lifted,” the email stated. “In light of recent events and also knowing these types of situations may cause students to experience heightened levels of anxiety, please take this opportunity to talk to your students about the importance of sharing concerns with building administration or other adults they trust.”

Students who had not yet eaten lunch were provided time to eat before returning to class, the email stated.

“We will also continue to make sure that students who need emotional support have access to appropriate services,” the email stated. “We will also have an increased police presence on campus throughout the end of the school day.”

A news release from the Kane County Sheriff's Office stated the empty shell casing "appears to be an isolated incident."

"The Kane County Sheriff’s Office school resource officer is working with school officials to investigate the incident in an attempt to determine where the casing came from," the release stated.