There was one minor injury Wednesday to a custodian cleaning up after one explosion.
KREM-TV reported that the teen confessed his role and said he acted alone.
Police described the contents of the bottles as common household chemicals.
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.
Spokane School District spokeswoman Terran 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.
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