Detectives said the body has been identified, but that information was not yet being released to the public.
The body was spotted at about 6 a.m., closing nearly a mile of a frontage road along the freeway almost all day. Detectives determined that the woman was a victim of a homicide.
"It's a long county road right here, and it's a semi-rural area right off the freeway. There's dirt to each sides of the roadway, so there will be an extensive search to see if there's any evidence anywhere around this deceased person," said Sgt. Joe Borja of the Riverside County Sheriff's Department.
Authorities have no leads and urged anyone with information to come forward.
"If they have any information, whether they saw a suspicious vehicle here last night, early this morning, anybody in an argument or confrontation," Borja said.
Anyone with information can call the Riverside County Sheriff's Department at (951) 955-2777.