Mrachek Middle School in Aurora, Colorado.

(Photo: Courtesy Aurora Public Schools)
Authorities in Aurora are looking for people who tried to detonate a pipe bomb outside a middle school.

The attempted detonation happened Saturday evening at Mrachek Middle School but the device wasn't found until Monday morning, prompting students to be evacuated.

Fire department spokeswoman Wendy Lippman said security video showed the suspects lighting the bomb in an alcove between two buildings. She said it just burned and didn't explode.

No other devices were found inside the school but classes were canceled for the rest of the day.