(CNN) -- What appears to be the outline of a child in a fetal position can be seen in a photograph of the trunk liner from the car driven by Casey Anthony, a Florida woman charged with killing her 2-year-old daughter, according to documents released in the case.
Caylee Anthony's skeletal remains were found near her family's home in December.
"A very interesting photo exists of the trunk liner ... which highlights the very large stain," FBI Intelligence Analyst Karen Cowan writes to a colleague in a September 2008 e-mail contained among nearly 1,000 pages of documents released Tuesday.
"If you look closely at this photo, there appears to be the outline or silhouette of a child in the fetal position. You can make out what may be the back, bottom and legs most clearly."
An FBI supervisory photographic technologist replied in a later e-mail, "We do not report conclusions about what may or may not have left any marks or impressions in cases like this -- it is too speculative. Others can draw their own conclusions about that." Watch Nancy Grace report on the documents »
Anthony, 23, is charged with first-degree murder in the 2008 death of her daughter, Caylee Anthony. Prosecutors have said they are seeking the death penalty against her.
The child's skeletal remains were found in December in a wooded area about a half-mile from the home where Caylee and her mother lived with Casey Anthony's parents. The cause of Caylee's death is homicide by undetermined means, authorities have said.
Police released documents this year showing they believed that Caylee was slain within days of the time she was last seen and that her body was in the trunk of her mother's car for "a period of time."
An attorney for Casey Anthony's parents, Brad Conway, released more documents Wednesday, according to CNN affiliate WESH. Among them were results of an FBI test that show fibers taken from duct tape found across Caylee's mouth do not match similar fibers from tape that was found on a gas can in the Anthonys' garage, the station reported.
"It was easy in the beginning to say, 'Well, you know, the duct tape on the gas can and the duct tape at the crime scene, they're similar,' and people draw conclusions from that," Conway said. "Now we have an FBI report that says they're dissimilar, that they're not matched. Now I think the view of the land is a little bit more accurate than it was six months ago."
In a May interview on CNN's "Larry King Live," George and Cindy Anthony said they believe that their daughter is innocent.
Other documents released Tuesday by authorities show that:
• Unidentified female DNA found on the duct tape on Caylee's mouth was matched to a female FBI agent involved in processing the site where the remains were found.
• A hair found in the trunk of the car is consistent with that being from a dead body, although authorities cannot say that for sure. The hair is also consistent with that taken from Caylee's hairbrush and is different from Casey Anthony's hair. An FBI agent says in an e-mail that it would be good to have more than one hair showing decomposition, if others are found, because there could be some "random possibility of why one hair would look like that."
CNN's Natisha Lance contributed to this report.