An unidentified male called the high school around 8:30 a.m. Sept. 10, saying he was upset with the school administration and would come to the building with a firearm, Jefferson Police Chief Paul Castimore said.
Authorities remain unsure if that was a confirmed threat or swatting incident.
The investigation will continue if and when new leads are developed, Castimore said.
"We realize that many rumors have been circulating throughout the community regarding this incident," he said. "All local leads have been exhausted and have since been forwarded to our federal counter partner."
Students were sent home out of an abundance of caution, he said.
"At no time was it felt that any student or staff was in danger based on the initial call to the school," the chief said.
Click here to follow Daily Voice Ridgewood and receive free news updates.