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EL MONTE, Calif. (KTLA) –A three-alarm blaze gutted the cafeteria building of a high school in El Monte on Monday morning.

The fire was reported around 2:30 a.m. at Mountain View High School, located at 2900 Parkway Drive.

The large building also houses a maintenance shop, a faculty cafeteria and a student store.

Firefighters began with an aggressive interior attack, but had to pull back into defensive mode due to a partial building collapse.

“The collapses of the facade and the interior roof were continuing throughout the incident, so it was absolutely unsafe to operate from within,” said Tony Imbrenda, a spokesman for the Los Angeles County Fire Department.

There were six ladder trucks and about 150 firefighters at the scene.

Fire crews fought to keep the flames from spreading to any other buildings. The cafeteria building appeared to be a total loss.

One firefighter suffered a minor back strain but was not transported for treatment.

The fire was knocked down just after 6:30 a.m., Imbrenda said.

A bulldozer was brought in to pull down burning embers, and crews remained on scene hours later to continue cleanup efforts.

It wasn’t immediately clear what may have sparked the blaze.

Investigators say it could have been a lot worse, had it not been for the Martin Luther King Jr. holiday.

“It was definitely a blessing in disguise for us today to not have school and deal with the influx of individuals coming into this scene,” said Imbrenda.

School officials say classes will go on as scheduled tomorrow.