Investigators trying to unravel the mystery behind the disappearance and death of 11-year-old Celina Cass searched her New Hampshire home again-- looking for clues that could show how she died.

An autopsy failed to provide conclusive evidence of how she died, and the investigators were waiting for toxicology results.

According to a Fox News report, the new search at her home may not provide all answers surrounding her death. But the report said that after an initial search, officers could conclude that foul play was suspected, judging from what they saw at the home.

Celina disappeared in the night of July 25. The next morning she was gone and the local police and the FBI launched a massive search operation to find her. Her body was fished out from the Connecticut River, near a hydroelectric dam between Stewartstown and the town of Canaan, Vt. on Aug. 1.

Celina's stepfather Wendell Noyes, who was the last person to see her alive, said she had been playing on the computer.

Police said there was no trace of any force being used, and her friends said Celina was unlikely to go with a stranger on her own volition.

Meanwhile, it was reported that Noyes checked himself into a mental institution on Thursday. A day before, investigators seized a pickup truck used by him as they searched for clues related to her death.

Celina was living with her older sister, mother and stepfather. Ever since her body was found in the river near her home, Celina's stepfather has been in public eye because of what has been described as bizarre behavior. He rolled on the ground face down, and an ambulance reportedly took him to the hospital. He was discharged on Monday, and was seen picking up cigarettes from a shop in town the next day.

It emerged that Noyes had a troubled past and that he had been medically discharged from the Air Force owing to mental illness.

He also had been arrested in 2003 for threatening an ex-girlfriend and was involuntarily institutionalized. But in this case, he was declared unfit to stand trial owing to his mental illness. However, the judge had noted that his mental illness posed "a potentially serious likelihood of danger to himself and others."

Police questioned Noyes in connection with the death of the child, but they have not named anyone as a "suspect" or "person of interest."