Sources close to the Casey Anthony case told Local 6 News on Thursday that they have overwhelming evidence showing that she intentionally killed her young daughter, Caylee, and was solely responsible for the toddler's death.

Anthony, 22, remains jailed on first-degree murder charges in her daughter's death. Caylee was 2 years old when she was reported missing in mid-July, a month after she had last been seen. Human remains discovered last month in a wooded area near Caylee's grandparents' home were identified as the missing girl.

Sources also said investigators have now established a time frame of death that dates back to June, according to reports returned by forensic botanists and entomologists brought in to anaylyze the terrain and insect growth where Caylee's remains were found. Sources said plants were growing through the skeleton and bug evidence was also recovered, both of which helped scientists reach their conclusion.

Orange County sheriff's detectives believe Anthony took actions that led to her daughter's death June 16, which corresponds to the June time frame of death, Local 6 News reported.

Investigators believe Anthony dumped Caylee's body around June 18 in the wooded area where the remains were found, sources said.

According to test results conducted on the trunk of Anthony's car by the Oakridge National Laboratory, the girl's body spent at least two days there before it was dumped, sources said.

A hair, which showed signs of decomposition, was also found in the trunk. Sources said the hair matches hair taken from Caylee's remains.

Sources said the time frame coupled with other evidence -- duct tape found over the mouth of Caylee's skull, high levels of chloroform detected in the trunk and cell phone pings from Anthony's phone that place her near the crime scene in mid-June -- points only to Anthony as the killer.

Although a cause of Caylee's death may never be known, sources said Anthony will be convicted based on extrememly strong evidence.

Investigators who initially thought that Caylee's death could have been an accident have changed their minds, sources said.

Anthony on Thursday was required by a judge to attend a hearing that centered around autopsy photos of Caylee. It was the first time Anthony had been seen by the public in months.

Watch Local 6 News for more on this story.