CHICAGO (CBS) — Classes were cancelled once again for Naperville North High School after another threat was made against the school.

At 9:18 a.m., Principal Stephanie Posey informed students and parents about the threat in a message on the school’s website.

READ MORE: Chicago Weather: Monday Brings Wind, Blast Of Cold Air

“Good morning Huskies, very regretfully there has been another threat against NNHS today. My heart is broken to alert you to a soft lockdown of the building with no movement to and from the building. The Naperville Police Department is here with us processing the situation and planning for the safety of all staff and students at North. If we must shorten our instructional day today, I will send you the process to follow for picking up students from the school, releasing them to their cars, or taking bus transportation home. At this time all students and staff are safe. To assist us with the process, please wait to come to campus as no one will be allowed to enter the building or grounds at this time. I will stay in contact with you as the morning progresses.”

The school, around 10:25 a.m., began releasing students in a staggered plan overseen by Naperville police; starting with student drivers and walkers followed by bus drivers. Parent pickup will occur at Door 19. No one is allowed to access the building once the plan was activated.

READ MORE: Multiple Juveniles Arrested During Large Gathering, Fights Near Millennium Park

This is the second time the school has cancelled classes in less than a month. On Sept. 22, District 203 in a Facebook post closed the school because of a previous threat.

The Naperville Police Department has determined that students and staff are safe, and that it is safe for the school to host its football game Friday night and homecoming dance Saturday.

MORE NEWS: Murray throws for 2 TDs, runs for 2 as Cardinals beat Bears

Police are still investigating.

CBS 2 Chicago Staff