By Steve Beck, Nicole Brewer, Mike Dougherty

LANSDOWNE, Pa. (CBS) – Fire officials believe two fires inside a Delaware County high school early Thursday morning were intentionally set.

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The damage is said to be so extensive that a fire chief says the school could be closed for the rest of the school year.

Fire crews responded at about 3:45 a.m. to Penn Wood High School on Green Avenue in Lansdowne.

Upon arrival, firefighters spotted the first fire located in the lobby of the school, which spread to several nearby offices. Firefighters were able to get that fire under control.

Moments later, an explosion was heard and firefighters found another fire near the rear of the building. Firefighters quickly moved their water hoses to that part of the building and were able to extinguish the fire.

During an inspection of the building, police officers found a door in the rear of the building that was pried open.

Fire officials are calling the fires suspicious.

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The damage to the building is so extensive that classes at the building could be canceled the rest of the school year.

“I think they’re going to have a hard time getting the school back up and running,” Lansdowne Fire Company Deputy Chief Wayne Worley said.

Principal Brandon Cooley says this was tough news to wake up to.

“We’ve had some bomb threats called in earlier this year, so it is very disheartening to see something like this happen,” Cooley said.

Classes were canceled for students in grades 9 to 12 on Thursday, as well as Friday.

Police hope surveillance video will help them figure out who is responsible.

The fires remain under investigation.

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