Detectives in Washington have recovered the remains of a girl, about 4 years old, whose body was hidden in a plastic tote.

Investigators with the Snohomish County Sheriff's Office believe she died at least four years ago.

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The circumstances surrounding the girl's death and the disposal of her remains are under investigation. She has not been identified. The cause and manner of her death have not yet been determined.

Authorities recovered the plastic tote Saturday after police served a search warrant at a home in Everett.

Detectives and investigators with the Snohomish County Medical Examiner's Office confirmed Tuesday that the tote contained the body of a young girl.

The sheriff's office began investigating the girl's death and disappearance in October after a relative said he or she was concerned about the girl's disappearance.

Relatives told officers they believed the child died at a home in Lynnwood while under the supervision of her biological mother.

Police said it was reported that the mother and her then-boyfriend had a history with law enforcement and "panicked" when they discovered the girl had died. Relatives believe the girl's mother and boyfriend wrapped her up, put her body into a storage container and kept it in their home until it began to decompose and smell.

Relatives told detectives they thought the couple poured concrete over the body in the container and kept it for several years, later stashing it at a relative's home after moving out of their own.

Police said the girl's mother told family members, including her other children, several versions of how the girl died.

She was never reported dead or missing to law enforcement and was never enrolled in any school. The last official record that showed evidence to her being alive is from September 2010, when she received an immunization.

No arrests have been made.

The sheriff's office is working with Child Protective Services and the Washington State Department of Social and Health Services in the investigation.