According to the department's news release:
The call was made around 10 a.m., and officials with the school and district decided to keep things operating as normal inside the school while locking the doors outside.
Authorities searched the school and its ground and found nothing or nobody suspicious that would have indicated a student's life was in danger.
Sun This Week says the lockdown lasted for about two hours.
The Rosemount Police Department is investigating.
The Rosemount Town Pages says elementary school students are on summer break now, and the high school went to shelter-in-place status while the search was being done.