There were also abbreviations of the Islamic State Organization "ISIS" on the walls of the educational institution.
Investigators, in cooperation with Hurricane City police, sent pictures of the information to the US Federal Bureau of Investigation for analysis.
"Based on the information we received from the FBI, we do not believe that this action was taken by someone related to the organization," the city police said in a statement.
She added that she was still following a number of indicators in the incident, but had not yet stopped anyone connected to the incident.
There are about 770 students in the American high school.