As crews searched for 50-year-old Sandra Coke, authorities discovered the body near Laguna Valley Park in unincorporated Vacaville on Friday. The body has not been identified.
Coke, an investigator for the public defender's office in Sacramento, was last seen leaving her Oakland home shortly after 8:30 p.m. Sunday. She reportedly told her 15-year-old daughter that she was meeting with someone who had information on her missing dog.
Coke said she would be back in 30 minutes. Her daughter called police when her mother did not come home that night.
Authorities found Coke's 2007 Mini Cooper convertible on Monday, just a few blocks from her home. Her cellphones were discovered near Interstate 80 in Richmond and near the Oakland-Emeryville border.
Oakland police have identified Coke's former boyfriend, Randy Alana, as a person of interest in the case. He and Coke were seen together Sunday, police said.
Alana, 56, of Oakland, a registered sex offender, was arrested on an unspecified parole violation on Tuesday. He is being held without bail.
Dozens of Coke's family and friends have announced a $100,000 reward for any information leading to her return.
"These last few days have been a living nightmare," said her sister, Tanya Coke-Kendall, who believes foul play may be involved.
The Associated Press contributed to this report.