Students in grades 6-12 in Two Harbors were kept out of school on Thursday as authorities investigated a possible threat to the school that was determined to be unfounded.

Lake Superior School District Superintendent Bill Crandall and administrators made the call shortly after 6 a.m. to close school for the day at Two Harbors High School. The Lake County Sheriff's Office identified one student, who was interviewed as a person of interest, Crandall said.

"It was determined there was no credible threat," Crandall said. "No gun on school property or even in the student's possession, and no arrests that were made."

Crandall said some students had already boarded buses by 6:30 a.m., when the decision was made to close school for the day. Those students were brought home before ever reaching the school.

High school principal Jay Belcastro was the first to learn of what Crandall described as "rumors," which he said started verbally before spreading to social media.

The decision to close school was made out of an abundance of caution, Crandall said, and to give time for sheriff's investigators to conduct their inquiry. Belcastro was the person who called authorities to investigate.

Schools across the country have been home to incidents of mass violence throughout the past 20 years. Active-shooter training has become a part of everyday life for American students.

Minnehaha Elementary School in Two Harbors and Silver Bay's William Kelley High School, also in the district, carried on the school days as normal.

"Unfortunately," Crandall said, "we've had other threats before and we worked collaboratively with our corresponding law enforcement agencies. It's a good relationship. A lot of times, we can diffuse the situation and get right to the crux. In this case, we just needed more time to come up with a determination."