Gruesome discovery: Girl's remains found covered in concrete inside plastic container

US Police have made the grim discovery of the remains of a child, believed to have died at least four years ago.

Detectives from Snohomish, Washington found the remains during a search of a mobile home last Saturday, according to KING 5.

Q13 FOX reports that the body inside the storage container was covered in concrete.

The Snohomish County Sheriff’s Office confirmed the body belonged to a young female, but her identity has not been made public.

A relative of the child (by marriage) expressed concerns about her disappearance to police in October, prompting an investigation.

Relatives believed the child was four-years-old when she died.

They reportedly told authorities that her death occurred while she was under the supervision of her biological mother.

"It was reported that the mother and her then-boyfriend (the two have since married) had history with law enforcement and “panicked” when they discovered the girl had died," the Sheriff's office claimed.

"Relatives believed that the girl’s mother and boyfriend had wrapped up the girl and deposited her body into a storage container.

"They kept her body in that container for some time in their residence until the girl's body began to decompose, at which point it is alleged that concrete was poured over the body in the container."

Court documents allege the child's mother made up stories about her whereabouts.

Authorities claim they are still investigating the circumstances surrounding the child's death and disposal of her remains.

The Sheriff’s Office claimed that in September 2010 the girl received an immunisation, which is the last official record of evidence of her being alive.

No arrests have been made and investigations are ongoing.