Washington (AFP) - The father and stepmother of a boy who was found behind a fake wall four years after he was reported missing made an initial court appearance in the US state of Georgia on Sunday.

Gregory Jean, 37, and Samantha Davis, 42, appeared in a Clayton County court near Atlanta on charges of obstruction, false imprisonment and child cruelty.

They were both denied bond, so must remain in jail for now, local media reported.

The couple were arrested, along with three juveniles, Saturday after police found the 13-year-old boy hidden behind a false wall in a linen cupboard of their home in Jonesboro, near Atlanta.

The strange case apparently started when the boy went to visit his father in 2010.

Police told Atlanta's Channel 2 the mother then reported him missing to child welfare authorities, but not to police, possibly because she was an immigrant and unfamiliar with the legal system.

Clayton County police were called to a house late Friday, but the occupants denied any knowledge of the child. Just to be sure, police searched the house. They found nothing, local media said.

But hours later police received another call and this time the boy was able to tell his mother where he was being held.

According to the Channel 2, the teen had found a cellphone and downloaded an app through which he contacted his mother, who was in Florida.

He was being hidden behind a panel in a linen closet in the garage, the news station reported.

"It shocked all of us, honestly," one neighbour said. "They were really nice people, they were open. They were like, 'Hey, come over any time you want.'"

Neighbours said the boy was seen at times working in the yard, and that they heard that he was home-schooled, reports said.

Jean and Davis were scheduled to appear in court again on December 9.