Valley High School Explosion In Santa Ana, Calif. (VIDEO)

A high school in Santa Ana, Calif. was briefly evacuated Tuesday morning when a boiler room explosion destroyed an auditorium on campus.

First responders with the Orange County Fire Authority began fielding calls at around 7:36 a.m. Tuesday morning about a structure fire at Valley High School. When they arrived on scene, they found that an explosion in the boiler room had caused significant structural damage to the auditorium, as well as a small fire.

Four students that had been near a wall next to the boiler room were transported to a local hospital for minor aches from the force of the blast, but otherwise there were no other victims near the area, said OCFA Capt. Jon Muir to The Huffington Post in a phone interview. In all, seven students were evaluated for minor injuries after the blast.

Muir, who was on the scene during the interview, was amazed that there weren't more victims from the blast.

"It's just amazing the amount of structural damage done to this building," he said. "It's fortunate that no one was hurt."

Video of the explosion, broadcast by ABC Los Angeles, shows that the blast lifted the roof of the auditorium off the building.

A bomb squad confirmed that there were no explosive devices on scene, and a hazmat team cleared the area. Investigators are combing through the evidence to determine the cause of the blast.

The campus was immediately evacuated after the explosion, but school was back in session by 8:30 a.m., said Muir. However, the area near the auditorium remains closed to students, and the graduation ceremony will be re-located to a different part of campus.

Valley High School has about 2,400 students and was founded in 1959, reports the Associated Press.

CORRECTION: A previous version of this story incorrectly stated that the auditorium is the site of a graduation ceremony. We regret the error.