The grandmother of a Florida toddler missing for more than a month disputes investigators' claims that they detected the scent of human decomposition in the trunk of a car used by the child's mother.

"Do me a favor," the grandmother, Cindy Anthony, said Wednesday. "Put a little piece of pizza or any piece of garbage in your car today and leave it shut up for 15, 16, 17, 18, 19 days in this heat and then come back to me in 19 days and tell me what it smells like."

Anthony's granddaughter, Caylee Marie, was last seen on June 9. The child's mother, 22-year-old Casey Anthony, is considered a "person of interest" in the disappearance and is currently jailed, trying to raise a $500,000 bond.

At Casey Anthony's bond hearing Tuesday, Det. Yuri Melich testified that the odor of "decomposition" was detected in the trunk of a vehicle used by the young mother.

"The smell I smelled was that of decomposition," Melich told the judge. He also testified that strands of hair similar to those of the young girl, as well as dirt, were found in the trunk.

Cindy Anthony disputed the decomposition testimony Wednesday after her daughter's lawyer revealed the family had received a tip that a child matching Caylee's description had been seen at the Orlando International Airport boarding a flight to Atlanta.

The tip was even more credible because the person reported that the little girl pronounced her last name the same way Caylee's grandparents say she does, attorney Jose Baez told FOX News.

Cindy Anthony said the tip was from a woman who lives in Orlando and was left on her voicemail. The grandmother said she called the woman back and they talked.

The caller claimed to have seen Caylee board the flight with an older woman. When she talked to the woman and child, the youngster apparently said her name was Caylee "Antony," pronouncing it without the "h" the way Cindy Anthony says her granddaughter does. When asked her age, the little girl said she was 3; Caylee is almost 3 years old.

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Prosecutors said Tuesday the case is beginning to look like a homicide.

Anthony's attorney said there is circumstantial evidence of a possible killing, but not enough to give prosecutors the confidence to charge her with homicide, kidnapping or any similar offense.

Detectives revealed that Anthony had become more of a focus of their investigation into her daughter Caylee's disappearance after they found the evidence in the trunk.

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When asked whether he considered the child's mother a suspect in her disappearance, Melich said he'd classify her as a "person of interest."

Melich also said a witness he interviewed remembered seeing bruises on Caylee's body and a mark under her eye without knowing that Melich had a photo showing similar marks on the toddler.

On cross examination, Melich admitted he didn't have any direct evidence that Casey Anthony played a part in her little girl's disappearance.

Investigators used cadaver dogs to search the child's grandparents' yard last week after a neighbor told them Anthony had asked to borrow a shovel around the time her daughter Caylee was last seen.

They previously have said that almost nothing Anthony has told them about her child's disappearance has checked out to be true. They haven't even been able to get information about the child's father, who Anthony has said is dead, Melich testified.

Also at Tuesday's hearing — held to argue over whether or not to release Casey from jail — the child's grandmother said her daughter is a good mom and hasn't committed a crime but has been dishonest before and has had trouble keeping jobs.

"Casey's lied to me in the past and when she's lied she's always told me the truth," Cindy Anthony said. "We've gotten to the bottom of the truth when I talk to her and spend time with her."

She told attorneys that her daughter is her "best friend outside my husband" and she had no reason to believe anything had happened to her granddaughter until last week because she'd "spoken to Casey on a daily basis."

"Without a doubt, she is a great mom," Cindy Anthony testified. "You can see it in her eyes. You can see it when they're together. There's nothing but love."

She said her daughter should be released from jail "because she hasn't committed a crime" and because she needs to help find Caylee.

Cindy Anthony speculated on the stand that someone was threatening her daughter and that's why she hasn't told the whole story about where Caylee is.

Earlier Tuesday, Cindy Anthony said Casey left the child in the care of someone she trusted, but that person betrayed her.

In an interview on FOX News Tuesday morning, she implied that her granddaughter might have been kidnapped.

Casey Anthony has been in prison since last week, when she finally reported her toddler daughter missing at her parents' urging. She was arrested on charges of child endangerment, making false officials statements and obstructing a criminal investigation.

Her attorney denies that his client has been lying to police and says she's been cooperating.

Cindy Anthony said Wednesday that 14 billboards across Florida, including two in Orlando, will show a picture of the missing girl. The reward for information leading to Caylee's return has been raised to $200,000, according to MyFOXOrlando.com.

Volunteers in the Orlando, Fla., area were continuing to canvass neighborhoods this week, distributing about 50,000 fliers, according to MyFOXOrlando.com.

Cindy Anthony said a family who had flown out of Orlando International Airport on July 2 had reported seeing a girl resembling Caylee. The girl apparently said her name was Caylee "Antony" — pronouncing it without the "h" — like the missing girl does, according to her grandmother. When asked her age, the girl said she was 3. Caylee is almost 3 years old, MyFOXOrlando.com reported.

Cindy Anthony said the woman who gave her the tip was to meet with Orange County Sheriff's detectives to produce a composite sketch of the woman seen with the girl.

Click here for photos of the bond hearing from MyFOXOrlando.com.

The Associated Press contributed to this report.