The Oro Valley Police Department responded to a telephone bomb threat made at 7:37 a.m. to Copper Creek Elementary School Thursday morning.
Police blocked off both entrances to Copper Spring Trail while a search was conducted by the Pima Regional Bomb Squad, detectives from the Oro Valley Police Department, and canine units.
Children were moved from the school to a grassy field on the north side of the facility.
Parents whose children were in school at the time were advised not to attempt to retrieve them.
The investigation concluded with no explosives found, but police have detained a suspect.
"A juvenile was taken into custody for questioning, and charges will likely follow," said Lt. John Teachout, a spokesman for the Oro Valley Police Department.
By 10:30 a.m., the school was deemed safe, and children are being allowed to return to class.
Because of the suspect is a minor, police did not release the identity.