There were no classes Friday at the Three Rivers Schools, in St. Joseph County, Michigan.

The district’s superintendent posted a letter to their website Thursday night informing parents that the schools had received three seemingly unrelated tips of potential threats within the district. That led to the decision to err on the side of caution and call off the school day Friday.

As a result of one of the tips, a student was questioned by police and later released to his parents. In a statement, the Three Rivers Community Schools said they take all threats seriously.