The body was discovered on Monday in a 1997 Mercury Marquis. Someone called police because the car was parked illegally on the 2000 block of Tustin Avenue.
"The car was parked in that driveway, blocking that driveway, and that's what was so bizarre about it all," said Costa Mesa resident Irene Williams. "Why was the car blocking the driveway?"
"Our officers got out to the scene, started looking into the vehicle and they got a foul odor coming from the passenger side," said Costa Mesa Police Sgt. Ed Everett. "The windows were down partially. As they began to look in the vehicle from the driver's side they saw what appeared to be a leg and a foot."
Police believe that that body may have been in the car as long as 10 months.
A 57-year-old former real-estate agent from Corona Del Mar had been driving the car with the body inside.
"At some point, all the fluid in the body drained out, the organs dried up and the heat in the vehicle basically mummified the body," said Everett.
The driver, whose identity was not released, told authorities she met the homeless women at a park in Fountain Valley in December. She let her sleep in the car and that was the last time she saw the woman alive.
Police say the driver claimed to be scared to report the death.
Autopsy results are inconclusive. There's no sign of foul play. the driver has not been charged with any crime.
"At this point we're still determining if we have a crime and if we do, what type of crime," said Everett. "There was an autopsy performed and there was no cause of death."
Anyone with any information about the case was urged to contact Costa Mesa Police at (714) 754-5252.
Authorities believe the deceased woman was in her 50s or 60s when she died. They believe she may have been about 5'4" to 5'6" in height, from the Fountain Valley area. They were told that her first name was "Signae."