The latest incident occurred Monday at Pine View High School in southwestern Utah, when an alert student noticed a backpack emitting smoke in a common area.
The teen was arrested on Monday night after a bomb squad investigated the school for two hours. Police also said the suspect had been researching information and expressing interest in ISIS and promoting the organization. Police said if the device had detonated, it would have caused significant injury or death.
In the vandalism incident, a USA flag was taken down from a pole in front of the school and graffiti reading "ISIS is coming" was spray-painted on a school wall, police said.
The flag and message appeared the day after a shooting at a Florida high school that killed 17.More news: US Aircraft Docked in Vietnam
"Based on our investigation we can confirm this was a failed attempt to detonate a homemade explosive", St. George police said in a statement.
Police also say that there were no "direct" threats made against the school itself and there were no other suspects.
Police said that Washington County Bomb Squad, Washington County Sheriff's Deputies and the Federal Bureau of Investigation responded to the incident to disarm the bomb.
Police delivered a search warrant at the home of the young male.More news: Watch a hotel rip Trump's name off its sign
OPP have give the all clear after a possible online threat towards Fellowes High School.
Someone emailed the dean of students about the comment, which was made Tuesday morning, and the student was pulled out of class and asked about the remark by the school resource deputy.
Fournier and police met to "review the note, examine the handwriting, consult the school cameras and the sign-out list of students who used the bathroom during "A" block". The bus driver reported it to police and the teenager was arrested on suspicion of making criminal threats.
The Washington County School District posted on its website that all of the school's students had been accounted for and were safe.More news: No age of consent: force must be proved in child rape
- Trump says he'll counteract any Russian Federation meddling in midterms
- How Manchester Utd came from behind to stun Palace 3-2
- Arrest warrant issued for Pro-Bowl Oakland Raider Aldon Smith
- Governor: Deal reached to end 9-day teachers' strike
- Antonio Conte hits back at Chelsea critics
- Warren Beatty and Faye Dunaway will return to present Best Picture
- Porsche unveils Mission E Cross Turismo EV study at Geneva show
- BJP usurped power through proxy in Meghalaya:Rahul
- High of 45 with strong winds in Boulder today
- The top ten billionaires are even richer than Forbes says