A threat of “possible gun violence” that authorities deemed credible forced classes to be called off Thursday morning across the St. Croix Falls School District in western Wisconsin.

The decision to cancel instruction — just as it was about to begin — and all after-school activities was made about 7:20 a.m. because of a “threat made that had some credibility,” said District Superintendent Mark Burandt.

Families started receiving word from the district soon after.

Burandt said law enforcement is investigating, and the “threat has been contained.”

“Assuming there is no new information, we will operate as normal [Friday],” he said.

A joint statement from police and the school district said “there was a threat, regarding possible gun violence made to our schools today. We became aware that this was a credible threat around 7:15 a.m.

“While the individual who allegedly made the threat was then taken into police custody, there were some other details that we felt needed to be clarified.”

Even with someone in custody, “in an abundance of caution, we decided it best not to have children in our schools today,” the statement continued. “We believe that this was an isolated issue.”

The district, which serves about 1,500 students, includes St. Croix Falls Elementary School, Dresser Elementary School, St. Croix Falls Middle School and St. Croix Falls High School.