PLYMOUTH (CBS) – Classes will take place as scheduled at Plymouth North High School despite a small fire that broke out inside a classroom early Monday morning.

The fire started just after 6 a.m., but was put out by the sprinkler system.

No students were inside the school yet. Some students and staff members who were in the parking lot were held in their cars and buses while firefighters investigated.

They were then sent to the performing arts center, school library, and classrooms that were safe to enter.

The Plymouth Fire Department said the fire does not appear to be suspicious. A cause was not released.

“We are thankful to the Plymouth Fire Department and our staff for their swift and efficient response,” the school said in a statement.