School officials evacuated Huron High School briefly on Wednesday after a student found a bomb threat written on a chalkboard.
The student found the note at about 11:15 a.m. It stated, "bomb" and "1 o'clock," police Chief John Majoy said.
Police and firefighters responded to the school, which was quickly put on lockdown while officers and school employees searched the building.
They didn't find anything, but activated the fire alarm to get everyone out of the building safely and speedily.
The students were outside for about 10 minutes, from 12:55 to 1:05 p.m., superintendent Fred Fox said. Once back inside the school, the students returned to their normal schedules until dismissal at 2:30 p.m.
Police are still trying to determine who wrote the message.
"It could have been written a day ago, a week ago or right before the student noticed it," Majoy said.