Authorities say the incident at the school at 1801 South Greenville Street happened just before 8 a.m. Surveillance video showed the explosion lifting the roof of the building. Fire officials say the building suffered significant structural damage.
Four people were hospitalized as a precaution: Three people had hearing issues, and one person was transported due to anxiety. Three other people were treated at the scene for minor injuries.
The boiler room is located between the boys and girls locker room. Orange County Fire Authority Capt. Jon Muir said no one was inside the building at the time.
"This was a very lucky situation where nobody seriously got hurt," Muir said.
Despite the blast, classes were able to start as usual, according to district spokeswoman Deidra Powell.
Surveillance video captured the scene at the school just after 7:30 a.m. The explosion practically ripped the roof off the physical education building.
"I was doing a report and then I hear a 'boom,' an explosion," said student Rodrigo Herrera.
"The walls shook, I was like, 'What happened?'" said student Carlos Pina.
Many students didn't know what to think: Was it an earthquake, or could it have been a bomb?
"After I saw metal all over the place, water pipes erupting, I was like either a bomb or something exploded," said Herrera.
The fire department says while they're not sure what caused the explosion, they think it was either mechanical failure with the boiler itself, or perhaps a gas leak. Whatever the case, the damage is extensive. The building is cracked in several places. The explosion ripped a door off.
"I was just turning on the computer when I heard this loud boom," said P.E. coach John Ferreida.
But Ferreida, like practically everyone else, is thankful that the boiler blew up before school started. If it had happened in the middle of the day, he says this could have been really bad.
"We're working with the school very closely to get a determination of what happened, what caused this, but I'll tell you that this was a very lucky situation where nobody seriously got hurt," said Orange County Fire Authority Captain John Muir.
The end of the school year is in two days. The school hopes to have repairs completed before the new school year begins in fall.