Time ran out Tuesday for a missing Florida toddler's mother to strike a deal in the criminal case against her, but it still isn't clear whether she'll be charged in the disappearance of her daughter, whom police say likely is dead.
Casey Anthony, 22, had until 9 a.m. Tuesday to tell investigators what she knows about little Caylee's disappearance in exchange for limited immunity. Anthony did not meet the deadline.
The withdrawal of the offer came after Orange County police said Caylee, who was 2 when she disappeared in June, probably isn't alive.
But without a body or sufficient hard evidence, filing charges in Caylee's apparent death has proven difficult, police told FOXNews.com.
"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 — a discovery that would significantly aid in the investigation.
"Obviously that would clear up a lot of questions that we have," Padilla told FOXNews.com.
He declined to comment on which of the various theories, if any, had become the most prominent in the investigation. Detectives have been trying to determine whether Caylee died accidentally, was killed or was kidnapped, as her mother has claimed. Police have expressed serious doubts about the abduction story.
"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 before 11 a.m. 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.
Anthony is back behind bars after her $500,000 bond was withdrawn over the weekend. Police now say they do not think her little girl is alive.
"We have scientific evidence back from the FBI lab," said Cmdr. Matt Irwin of the Orange County Sheriff's Office. “We have other evidence we have not yet released publicly. All of that ... leads us to believe Caylee is deceased."
Detectives theorize that Casey Anthony had been driving around with her dead daughter in the car sometime before she reported her missing July 16.
"There’s evidence to suggest there was a body in the trunk of Casey’s car and that body was Caylee’s," Orange County Sgt. John Allen said Sunday.
The statements are based on FBI forensics tests that confirm there had been a decomposing corpse in the Pontiac Sunfire driven by Anthony.
Detectives disclosed at a July hearing that Anthony's trunk contained strands of hair appearing to belong to Caylee, as well as a strong odor and a suspicious stain that glowed under black light.
Casey Anthony, who had been free on bond since Aug. 21 and out on house arrest, returned to custody Friday on new charges in an unrelated check fraud case. On Saturday Tony Padilla, the California bondsman who had posted the $500,000 in the hopes that she would help in the search, withdrew the bond.
"The new charges, increased security concerns and some of the new DNA evidence that’s come in put the bond at risk," Tony Padilla told FOXNews.com.
Anthony's attorney Jose Baez questioned the "reliability" and "accuracy" of any test leaked to the media by law enforcement.
"I won't comment on the specifics of any report I have not had the opportunity to review or have challenged by independent experts," Baez said in a statement.
Anthony has been named a person of interest in her daughter Caylee's disappearance, but has only been charged with child neglect and lying to authorities in the case. The check fraud investigation is unrelated.
She has told detectives that she left her little girl with a baby sitter and hasn't seen her since, but police don't believe her and say they haven't been able to find the sitter.
FOX News' Catherine Donaldson-Evans and The Associated Press contributed to this report.