A female body was discovered Friday afternoon in the area where California authorities were searching for a missing federal criminal investigator.

The body, which has yet to be identified, was found at about 1 p.m. in the area where officials were looking for Sandra Coke, who was reported missing since Sunday. Coke went missing after following a tip on her stolen dog.

Based on additional information obtained by the Oakland, Calif., Police Department, detectives decided to move their search-and-rescue location from the Vallejo, Calif., area to Lagoons Valley Park, an unincorporated area just outside of the city of Vacaville, Calif., according to Solano County Sheriff's Office Deputy Daryl Snedeker.

For now, authorities have called off any additional searches.

Earlier, registered sex offender Randy Alana, 56, was identified as a person of interest in Coke's disappearance.

Investigators believe Alana and Coke were together the night she went missing, according to the Oakland Police Department.

Alana is registered as a high-risk sex offender with a criminal history that includes kidnapping and rape, according to the state's database.

He and Coke dated more than 20 years ago, Coke's friend Dan Abrahamson told ABC San Francisco affiliate KGO-TV.

"He reappeared in the Bay Area rather recently and reached out to Sandra for help," Abrahamson told KGO-TV.

Alana was taken into custody on an unspecified parole violation Tuesday and is being held in the Santa Rita Jail in Dublin, Calif., without bail, according to Alameda County online records. He is scheduled to be arraigned in Alameda County Superior Court on Aug. 16.

Meanwhile, investigators overnight launched a massive search at the Solano County Fairgrounds in Vallejo, Calif., for signs of the missing woman, KGO-TV reported.

Coke was last seen at her home Sunday by her 15-year-old daughter. A spokesperson for the family said she left the house to follow up on a lead related to her missing dog.

"There's no question something had happened. There's no way she would have ever left her daughter there alone," Wendy Springer, Sandra's best friend, told ABC News.

For weeks, Coke had been looking for her beloved dog, Ginny, who disappeared after someone broke into her home in May. Coke offered a $1,000 reward on "missing" posters. Tips were called in, but they all were dead ends.

This past weekend, Coke discovered a new lead in finding Ginny.

"She told her daughter that someone called about the dog," her sister Tanya Coke said.

Coke's family said she left the house to meet the caller, hoping to be gone for a half hour, but never returned. Coke's daughter then tracked her mom's work and personal iPhones using a GPS application. Both had apparently been dumped: one on a Richmond, Calif., Highway, the other near Oakland, Calif.

"The phones were still working the next morning, sending a signal," Tanya Coke said.

Police found Coke's Mini Cooper two miles from her home.

"It's absolutely heartwrenching," Tanya Coke said. "Every parent, every sibling's nightmare. It's especially upsetting that she might be in danger and that there is foul play here."

On Wednesday, investigators took bags of evidence from Coke's home, including her laptop computers, hoping to find clues.

Police won't say if they believe Coke's work helping win release for inmates on death row, or the search for her missing dog, have anything to do with her disappearance.

"She was very attached to the dog and very concerned about trying to get her back," said Joe Schlesinger, a friend for over 20 years.

Schlesinger and Coke work with death-row inmates in the Office of the Federal Defender for the Eastern District of California.

"We work on cases where there are all kinds of tragedies and it isn't the most popular work, but we have no reason to believe her disappearance has anything to do with the crimes she was investigating," said Schlesinger. "She was a committed, stable person that wouldn't just wander off."

Coke's family and friends are vowing to keep searching until they find her.

"She's a very special person," Springer said, "unusually kind and generous and big-hearted."

Coke was described as 5-foot-6 and 150 pounds, with a medium complexion, brown hair and brown eyes. She was wearing a black-and-white shirt and dark jeans when she disappeared.

Anyone with information on her whereabouts is asked to call the Oakland, Calif., Police.

ABC News' Gio Benitez and Josh Haskell contributed to this report.