Missing Florida toddler Caylee Anthony likely is dead based on evidence suggesting her decomposing body had been in the trunk of her mother's car, the Orange County Sherriff's Office said Monday.

A statement issued to The Associated Press said that the forensics tests confirmed there had been a decomposing body in the Pontiac Sunfire driven by 22-year-old Casey Anthony, who is behind bars again after her bond was revoked over the weekend and new check fraud charges were filed against her.

"(FBI) laboratory evidence, along with additional evidence that has not been made public, leads investigators to the belief there is a strong probability that Caylee is deceased," the sheriff's office told the AP on Monday. "If any evidence to the contrary is provided, it will be vigorously pursued."

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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.

Representatives from the Orange County Sherriff's Office were not available for comment Monday evening.

But protesters and supporters refused to give up on the prospect that the missing girl was still alive, as they descended on the Anthony home Monday, some saying they wanted to help the family find the missing toddler.

Protester Erika Courtney claimed Casey Anthony's parents and brother were covering up for her. Courtney banged on the Anthonys' door and demanded that the family tell the truth.

"I am here to speak for little Caylee," Courtney told MyFOXOrlando.com. "They know the truth."

Courtney said she plans on continuing her protest despite a trespassing warning issued by Orange County deputies.

Casey Anthony, who had been freed on $500,000 bond, returned to custody Friday on new charges in an unrelated check fraud case. On Saturday Tony Padilla, the California bondsman who had posted the money 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," Padilla said in a telephone interview with FOXNews.com. He declined to say what DNA evidence led to the decision to withdraw the bond.

Orange County Sheriff's Office Sgt. John Allen told MyFOXOrlando.com Sunday that evidence suggested there was a dead body in the trunk of Anthony's car.

He said they expect more test results from FBI officials soon, but declined to identify the evidence.

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.

Her 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.

Click here for a timeline of the case.

Click here for more on the protests from MyFOXOrlando.com.

Click here for more on the evidence from MyFOXOrlando.com.

The Associated Press contributed to this report.