Authorities in Peoria are investigating the discovery of possible human remains found near mile marker 17 on Highway 74.
City residents called Peoria police about 1 p.m. Wednesday to report they saw a body on desert land close to the highway.
Police spokeswoman Amanda Jacinto says the remains appear to be skeletal and "they have been exposed to the elements for quite awhile."
Thursday, detectives determined the bones were that of an adult female, and may have been there for a couple of years. Forensic experts are trying to identify the victim.
A cause and manner of death haven't been determined.
The Associated Press contributed to this report.