Students attending Mahtomedi High School and the district's middle school went back to e-learning Wednesday after a threatening message was sent electronically to the east metro district's tip line.
The message targeted an individual at one of the secondary schools and included a specific date — Wednesday — Superintendent Barb Duffrin wrote in a letter to families and staff that was later posted online.
The district contacted the Washington County Sheriff's Office, which began an investigation, she wrote.
"We know this is upsetting and disruptive to the important teaching and learning that happens in our schools and that for some students this news can cause increased anxiety and worry," Duffrin wrote. "Please know that administration and staff are actively planning support for our secondary students upon their return to school."
The e-mail also asked anybody with information about the threat to contact the district.
