GREELEY, Colo. (KKCO) - Greeley police said officials haven't determined if Kayleah Wilson ran away or was abducted.
She disappeared after leaving her home to walk to a birthday party in Greeley.
Amber Alerts go out instantly via text to cell phone subscribers and to radio and television stations.
They are also posted on electronic highway signs to alert motorists.
Criteria for Amber Alerts include information that a child may be in danger or vehicle and suspect descriptions.
Colorado's Amber Alert managers say the criteria are there so that the public doesn't ignore alerts when too many are issued.