Police say the incident happened at about 8:30 a.m. after someone mixed chemicals together inside four plastic soda bottles. The pressure inside built up until the bottles exploded.
Only a small number of students heard the blast. Moments later school leaders spoke the the school.
"The intercom came on and he was just like, 'This is a lock down, this isn't a drill' and we were just thinking it was a drill," said Ryan Shams.
Thirty-five police officers scoured Bountiful High School for other explosive devices. None were found.
Three others were discovered outside the school. Two were located two jut off Wall Street and one in an LDS church parking lot.
Bountiful Police say they had the suspects in custody and they were conducting interviews to discover what happened.
A Hazardous materials crew was dispatched to the scene, although no injuries were reported.
Police say 18-year-old man named Chris Perry and a 16-year-old girl.
Perry is charged with four class two felonies, punishable with up to 15 years in prison.
The lockdown continued for about an hour and a half.