Classes at Chaska High School were canceled Tuesday after the school was locked down in the morning because of a threat.
"CHS received a threat this morning. We have taken it seriously and are now working with police," the school said.
Freshman Bailey Van Eyll said she and others in the school of about 1,250 students were immediately ushered into a computer lab when they got to school.
Van Eyll and her classmates sat silently on the floor in the dark for three hours, texting updates to their parents until getting the OK to leave.
"We were all scared," she said. "I don't really know what happened."
Police guarded both entrances to the school during the lockdown.
A police sweep of the high school and parking lot came up empty, School District spokesman Brett Johnson said.
Johnson declined to reveal details of the threat, adding, "We're concerned about copycat things."
