Washington state authorities are investigating the mother and stepfather of a 4-year-old missing for at least four years after the girl’s remains were found in late October hidden in a plastic cooler and encased in concrete, possibly to hide the rotting smell, PEOPLE confirms.

The couple has not been charged and Snohomish County deputies don’t know how the girl died, but in a search warrant affidavit obtained by PEOPLE, authorities allege her mother and stepfather kept her death a secret.

Police have not publicly identified the girl, her mother or her stepfather.

The little girl’s remains were discovered after relatives reached out to authorities in late October after growing concern over her disappearance, according to the affidavit.

The affidavit alleges the mother’s story to her family about the girl’s disappearance changed several times: At first, she allegedly said the girl died of medical causes. Then, she allegedly said the girl went to live with her grandmother. Finally, she allegedly said the girl died while taking a bath, and that the couple — who married after the girl died — panicked and hid her body instead of going to police.

Before she went missing, the victim’s mother allegedly told relatives her daughter had autism, the affidavit states. Relatives remember seeing the little girl hitting herself in the head and wearing a helmet on several occasions, according to the affidavit.

During their interview with police, the relatives said they remembered a strong odor in the the couple’s apartment soon after the girl went missing.

When they made a remark about the smell, the girl’s mother allegedly blamed the neighbors, who she said were into fishing.

In the affidavit, authorities speculated that the couple allegedly poured concrete to conceal the smell of the body.

“Pouring liquid cement into a container with a body would assist greatly with containing the odor— and conceal the body,” the affidavit states.

One relative alleged that once, the girl’s mother asked her to help move the cooler, but when the relative put her hand on the lid, the mother put her foot on top of the cooler and warned her not to open it.

Apparently there are no lengths that a parent would go to in order to protect themselves from their crimes against their children. I had actually never thought about the whole concrete thing. Yes I’ve heard of adults doing that to other adults but I never thought about a child being placed in a cooler and concrete being poured around it to seal in the odor. How creative.

It is unfortunate that they aren’t releasing the information. Because as of yet I cannot determine whether or not this child was reported missing to the public or whether it was just a lie that she kept within the family. It would be great to put the public at ease. We really get invested into these stories. They really do touch our hearts and we really really do have a lot of concern for these children. So when a body is found or any updates or discoveries take place we are the ones who are sitting by the sidelines. We are literally waiting to hear anything. And as a blogger I feel like it is my responsibility as well as many other bloggers to alert the public. I just wrote a similar story about this the other day. The positive thing is these crimes are making their way to the surface and these parents are going to be charged. Someone will be held accountable.

Will concrete throw a dog’s scent off the trail? If a cadaver dog is searching around your property and you have your child buried in concrete would a dog pick that up?