Bomb Left Outside Colorado Police Station

The FBI is trying to determine why someone left an explosive device in a backpack in front of the police department of a small Colorado mountain town.

A Nederland, CO, police detective found the bag outside the building when he began his shift Tuesday morning and brought it inside because he thought it was lost property. He opened it and found "suspicious articles" that were later determined to be an improvised explosive device, police Marshal Paul Carrill said.

The FBI, which had assumed control of the investigation by Wednesday afternoon, said the device was active but failed to detonate. Two robots searched the backpack, and multiple pieces were removed from the device and sent to a forensics lab, the Associated Press reports.