A spokesman for the FBI in Minneapolis said the bureau was aware of the tweet. As of Monday afternoon, the teacher had not been charged with a crime, the Star Tribune reported.
Mark A. Zurek, superintendent of Independent School District 917, wrote on the district's website that a complaint about an employee was received over the weekend and that the teacher was placed on paid administrative leave "pending the outcome of the investigation."
School district officials said the teacher is a paraprofessional, WCCO reported.
The tweet was published hours after Kavanaugh was sworn in as Supreme Court justice after contentious confirmation hearings that included allegations of sexual harassment.
Brett Kavanaugh Confirmed by Senate to U.S. Supreme Court