An eight-year-old girl was allegedly kept locked inside her home throughout her whole life by her own mother and grandparents in Germany.

The girl, identified as Maria, had been kept locked away at a house in Attendorn, Cologne, since she was less than a year old. According to local media reports, the girl is so physically underdeveloped that she cannot even climb a flight of stairs.

The girl's father had reportedly been looking for her for years. She was freed after the family's neighbours tipped off the police in September.

Her parents had already been separated at the time of her birth. The father received a note from her mother stating that the family was moving to Italy with their child, who was then six months old.

But they had not really left. In 2015, her father approached the police, claiming that he had seen his wife and their daughter in Attendorn multiple times. Maria's maternal grandparents were then questioned by the police but managed to get away with it.

Maria is believed to have spent most of her life confined to a single room at her grandparents' house. She did not have any signs of physical abuse or malnutrition, but she is severely underdeveloped.

It is still unclear why the mother kept her child hidden for years. The mother and grandparents have refused to give any details.

The investigators believe that she has not seen daylight since she was a toddler. The girl told the authorities that she had never seen a forest before, been in a meadow or driven in a car.

"She can't have managed to get much of a glimpse of the outside world," local newspaper Sauerland Kurier quoted prosecutor Patrick Baron von Grotthuss as saying.

The prosecutor has charged the mother with deprivation of liberty and mistreatment. Her grandparents are also being investigated by the local authorities.

Crime Scene police line
Crime scene police line | Representational Image Photo: GETTY IMAGES / SCOTT OLSON