NEDERLAND, Colo. (AP) — Federal investigators worked with the Boulder County bomb squad after a possible explosive device was left in front of the Nederland Police Department.

Denver station KCNC-TV reports a detective found a backpack outside the building when he began his shift Tuesday morning. He brought the bag inside and found what appeared to be an improvised explosive device.

Two robots searched the backpack, and multiple pieces were removed from the device. The pieces were sent to the forensics lab in Boulder.

Station KMGH reports that police official Paul Carrill said “there was a true threat here.” But he added that he would leave it to the county bomb squad to provide details on the device. Official spokesmen for the Boulder County Sheriff’s office did not immediately return an Associated Press call for further details.

The police department is in the mountain town’s main retail complex, which includes a grocery store and multiple shops. Those businesses were evacuated.

Nederland is located about 15 miles southwest of Boulder.