SPOKANE, Wash. (AP) - Two plastic pop bottles filled with chemicals exploded inside Ferris High School on Wednesday, prompting officials to evacuate the school and search the campus. Investigators later identified a student they said was responsible.
There was one minor injury.
Investigators quickly targeted a male Ferris student who they say admitted to his role in the explosions, KREM-TV reported. Officials said he acted alone.
The teen was released to his parents, who were described as cooperating in the investigation.
In a post on Twitter, police called the incident "more of a malicious mischief nuisance than any threat to students." Police described the contents of the bottles as common household chemicals.
"These devices are not all that uncommon," Spokane Police Capt. Brad Arleth told KXLY-TV. "It's not common for us to have two in one day at a school. However, I do want to emphasize these type of items are not inherently dangerous."
Spokane School District spokeswoman Terren Roloff said this is finals week at the school on Spokane's affluent South Hill area.
"This is a very common strategy to get out of school," Roloff told KREM-TV.
She said the first explosion was considered a minor nuisance so the school was not immediately evacuated.
The first bottle blew up around 8 a.m. in a hallway, school officials said. About three hours later, a second device exploded in the school commons as emergency crews examined the liquid in the first bottle.
The school began evacuations after the second explosion.
The Spokane Fire Department reported that a custodian suffered skin irritation while cleaning up after the first explosion.
Police and fire personnel searched the school and campus but found no other devices.
Officials said classes would resume Thursday.
(Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)
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