ORTONVILLE, Mich. -

Brandon High School was evacuated Thursday after a written threat was found in the building.

In a message to parents, Principal Celeste Nowacki said students were taken to the Harvey Swanson football field by bus.

"A thorough sweep of the building is underway with Oakland County Sheriff. Due to the estimated duration of the investigation, students who normally ride the bus will be transported home early. Students who drive will have access to their cars and will also be released early. Parents who wish to pick up their students may do so at the Harvey-Swanson athletic complex," said Nowacki.

Parent-teacher conferences have also been delayed for one hour.

The high school is located at 1025 S. Ortonville Road in Ortonville.

Stay with Local 4 News and ClickOnDetroit.com for updates to this developing story.