Students are being asked to stay home from their Delaware County high school after someone broke into the building overnight and set at least two fires.
And, firefighters say the blazes that broke out inside Penn Wood High School -- Green Avenue Campus in Lansdowne were likely intentionally set.
"Fire doesn't start itself," said Deputy Chief Wayne Worley. "We're just not sure how the fire got so far ahead of itself."
Worley says an automated firm alarm went off around 3:45 a.m.
"Upon arrival.. we had fire in the lobby It spread out throughout the first floor into the offices."
Firefighters were able to put out that blaze but a search of the building showed another fire in a classroom on the north side of the building that "was obviously set," Worley said.
The damage appears extensive and the building likely won't be repaired until next school year.
Principal D. Brandon Cooley told NBC10's Tim Furlong that the Green Campus, which houses 11th and 12th graders, could be closed for the "foreseeable future."
Classes were canceled for Thursday and Friday not only at Green but also the Cypress Street Campus that house ninth and 10th graders, according to a message posted to the William Penn School District website. Classes will also be canceled on Monday and Tuesday. The students will return to class Wednesday and will follow a "modified schedule" at the Cypress Street Campus. Details of that schedule will be sent to parents via the school's telephone notification system on Monday.
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In a press release, school district spokeswoman Pamela Bookman said that the Cypress Street school in Yeadon will likely serve as the school for all students for the rest of the school year utilizing a yet-to-be-determined modified schedule.
There were no reports of any injuries.
Police sources told NBC10's Deanna Durante that the school has recently dealt with a series of bomb threats. Investigators are reportedly looking into this act of arson possibly being an escalation of those threats.
Fire investigators along with state police were pouring over surveillance video to see if they could find those responsible for setting the blaze, Worley said.
As for the students, especially the 12th graders, they are left with no school to go to.
"It's really disappointing when you think about it... it’s your senior year, your last year in high school. You really expect everything to go out on a positive note," said senior Trey Barnes.