Searchers didn't give up on finding missing tot Caylee Anthony Wednesday in spite of scant numbers and the dismal news that she is now feared dead.

As the hunt for the Florida toddler stretched into a fifth day, EquuSearch volunteers said they're more determined than ever to find her, even though police said earlier this week they don't believe Caylee is alive.

The 30 to 40 people combing the Orlando area for Caylee, who would have turned 3 last month, are "not pulling out until they find this baby or exhaust every lead," search director Mandy Albritton told the Orlando Sentinel.

Emotions were running high, she added.

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Meanwhile, the little girl's mother remained behind bars since her latest arrest on unrelated check fraud charges and the withdrawal of her $500,000 bond. A visit with her parents was planned Thursday morning.

Time ran out Tuesday for Casey Anthony, 22, to strike a deal in the criminal case against her. She has pleaded not guilty to lying to investigators and child neglect in connection with Caylee's disappearance.

Without a body or sufficient hard evidence, filing charges in Caylee's apparent death has proven difficult, police told

"That's still a possibility," Orange County Sheriffs' spokesman Carlos Padilla said when asked whether Anthony could face charges in Caylee's death. "But we don't have that right now."

Padilla said the focus is still on finding Caylee — alive or dead.

"Obviously that would clear up a lot of questions that we have," Padilla said.

Anthony could have received limited immunity in exchange for telling investigators what she knows about her missing child had she met with prosecutors by 9 a.m. She declined, and the State Attorney's Office withdrew the offer.

Padilla wouldn't elaborate on which of the various theories about what happened to Caylee detectives were focusing on. Previously, investigators have said the child might have died accidentally or been killed.

Anthony has insisted a baby sitter ran off with her little girl. Police say they haven't been able to find the sitter and doubt she even exists.

"The key is with the mother, with Casey," Padilla said. "If there is a cover-up, it would be her — if there is. Right now she continues to not provide any information that is helpful to us."

The State Attorney's Office brokered the immunity agreement for the young mother — which would have ensured that any information she gave prosecutors could not have been used against her in court. Evidence gathered based on the details she provided could have been used, however.

"As of this morning, the state has not heard from the defense attorney regarding our offer to speak about the case," the State Attorney's Office said Tuesday. "The offer has now expired."

Police haven't been permitted by Anthony's lawyer to interview her about Caylee's whereabouts in some time, according to Padilla, though they did speak to her about the alleged check fraud that led to her second arrest Friday night.

Detectives theorize that Casey Anthony had been driving around with her dead daughter in the car sometime before she reported her missing July 16.

Scientific evidence from the FBI lab "leads us to believe Caylee is deceased," said Orange County Sheriff's Cmdr. Matt Irwin, and suggests "there was a body in the trunk of Casey's car and that body was Caylee's," according to Sgt. John Allen.

The FBI forensics tests confirm that there had been a decomposing human corpse in Anthony's Pontiac Sunfire, where DNA from strands of hair and a stain were matched to Caylee, police said.

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FOX News' Catherine Donaldson-Evans and the Associated Press contributed to this report.