Two days after disappearing, a toddler was found dead under the couch of her own home.

At 6:30 pm last Tuesday, 16-month-old Semaj Crosby was reported missing by her family.

Just hours before she went missing, Semaj had been seen by the Illinois Department of Children and Family Services, who were investigating her mother for neglect, but found no threat to the little girl’s safety.

She had been playing with her two siblings, and when she was reported missing, authorities hoped she had simply wandered off and would be found safe within hours.

Police and local volunteers rushed to help, launching a search of the town in the Joliet Township near Chicago.

They spent a day and a half searching for the little girl, going door to door and using bloodhounds to track her scent. More than 80 emergency personnel from the sheriff's office helped in the search, and a helicopter conducted an infrared air search of the area.

But two days later, just after midnight last Thursday, Semaj's body was found under the couch of her family home.

According to the Chicago Tribune, the family home was in a "deplorable condition" and was often inhabited by squatters.

The cause of Semaj's death is as yet undetermined, with police awaiting further investigations and toxicology reports. Police have called her death suspicious.

Police and FBI agents were only granted access to search inside the home hours before Semaj's body was found. The 16-month-old's body was reportedly found under a couch in the home, which "did not have legs and was flush with the ground".

"Having kids of my own...it's tough," deputy chief of the Will County sheriff's office, Rick Ackerson, told reporters.

He also said that as many as five to 15 people lived at the home at any one time, with several people living inside the home the week Semaj had died.

"We will continue to try to find out why it ended in such a tragic end," he said.

Neighbour Maria Jones, who lived just two houses from where the 16-month-old was found told the Chicago Tribune she was "distraught" over the news.

"We were out here looking for two days and to find out that the baby in the house..." she said.

An attorney representing Semaj's mother, Sheri Gordon, says she is "extremely distraught" over the death of her daughter.

"She prays for her daughter and appreciates the community's support," the attorney, Neil Patel, said in a written statement on Facebook.

"We look forward to when we can put this tragic incident behind us and allow the healing to begin."

The house has since been deemed "unliveable" by authorities, with CBS Chicago reporting investigators found the home "heavily soiled" with a "serious degree of filth".

Rooms were found with broken cabinets and garbage all over the room, with bedroom floors covered in "large amounts of clothing, bags and junk".