Cambridge-Isanti schools were shut down Wednesday while authorities investigated a possible threat made on social media that turned out to be not credible.

Authorities became aware of the posting on Snapchat early Wednesday morning and decided just before 6 a.m. to close all schools and cancel after-school activities.

"Due to the timeline of the information received and the need to fully investigate, the decision was made to take precautionary safety measures," said Superintendent Ray Queener.

"In an abundance of caution, we also canceled all of our evening activities. This has been a thorough investigation; at this time no credible threat has been identified," he said. "Our schools are safe."

The posting was vague, Queener said, but led them to believe that the threat was directed at the high school.

Authorities talked to about a dozen students and their parents but none of the students had access to weapons.

Cambridge Police Chief Todd Schuster said "it's extremely hard" to tell what is credible and what is not.

Police will be on hand when school opens on Thursday.

The decision to close the schools was announced on the district's Facebook page about 6:30 a.m. Buses were en route to pick up students but no one was in the school at the time. Parents were called to pick up some elementary schoolchildren who were at the Adventure Club.

Among the canceled events was a girls' playoff basketball game that Cambridge-Isanti was to have played at Forest Lake. It was moved to 7 p.m. Thursday.

The incident had schools in the neighboring district of Braham on alert. Extra police were on hand at both the high school and elementary school.

At Zimmerman High School, one student was arrested Wednesday after another student overheard him making threatening comments in class, authorities said.

School was not disrupted and the student was being held in a juvenile detention facility.

Staff writer Tim Harlow contributed to this report.

Pat Pheifer • 612-673-7252