Pleasant Hill police say a post appeared on the social media site Yik yak, threatening a shooting at the school.
They don’t have any suspects just yet. But more officers will be at the school Monday.
Yik Yak has also been blocked from students.
The threat comes after a Drake University freshman was arrested when police say he made a threat on Yik Yak.
Michael Crisp faces first degree harassment charges after said he was planning to open fire at the university.
The Yik Yak app doesn’t require users to identify themselves but it does track IP addresses.
With the help of the site’s administrators and the university, police were able to find Crisp in his dorm room.