Los Angeles County sheriff's spokesman Steve Whitmore said the department was notified by an individual who noticed a Mercedes appearing to match the description of Fiore's car about 12:42 p.m. in the parking lot of the grocery store in the 8600 block of Santa Monica Boulevard.
"They noticed the car was dusty, dirty, had no license plates and looked out of place," said Whitmore, adding that he could not confirm whether it was Fiore's car.
But the sources, who asked not to be identified because of the ongoing investigation, said the vehicle's identification number matched that of Fiore's white 2007 Mercedes CL S550. Buena Park police retrieved the car but would not immediately say whether it contained any evidence related to the slaying.
Detectives are trying to figure out where Fiore was killed. Authorities plan to review surveillance video around the parking lot to see if they can determine who left the car there.
Police allege that Fiore was killed Aug. 15 by Ryan Jenkins, her former husband and a contestant on the reality TV shows "Megan Wants a Millionaire" and the third season of "I Love Money."
Jenkins was found hanged in a motel room Sunday in British Columbia, following an international manhunt that included a high-speed boat chase in the U.S. and Canada.
Fiore, 28, was last seen Aug. 13 when she and Jenkins went to an upscale Del Mar hotel together. Jenkins checked out of the hotel the next morning, apparently alone, according to Orange County prosecutors.
The next day, the Canadian national called authorities to report Fiore missing, and within hours the body of a woman was found stuffed in a suitcase that was discarded in a trash bin behind a Buena Park apartment building.
Authorities said her teeth had been pulled out and her fingers cut off. Fiore was identified through a serial number on her breast implants, the Orange County district attorney's office said.
In addition to its gruesome nature, the case raised questions about how a man with a record of domestic violence got onto a show on which the object is to marry a woman.
Fiore and Jenkins had married earlier this year and quickly had the marriage annulled, although they were still dating.
During the investigation, information surfaced about previous domestic violence incidents involving Jenkins. In April, he was charged with "battery constituting domestic violence," according to court documents.
Detectives are investigating whether Jenkins got help disposing of Fiore's body and whether others aided him after she was slain. They have said finding Fiore's car would help in that part of the probe.
Jenkins was on the run for more than a week, slipping into Canada on Wednesday. According to the manager of the motel where Jenkins' body was found, a woman in her 20s signed for the room Thursday evening and left about 20 minutes later.