A 17-year-old girl managed to escape and tell police her 12 brothers and sisters were being held captive by their parents.
Riverside County Sheriff’s Department investigated, ABC News reported, and found the rest of her siblings in a dark and foul-smelling room.
The children’s parents were unable to provide a logical explanation as to why the children were restrained in the house, in Muir Woods Road, Perris, California.
One neighbour told ABC news: “They were very very pale-skinned, like they had never seen the sun. It was mostly girls, they were tiny, they looked a little malnutritioned [sic].”
David Allen Turpin, 57, and 49-year-old Louise Anna Turpin were interviewed and taken to a detention centre.
Police said the victims, six adults and seven children, appeared to be malnourished and very dirty.
They were given food and water after telling police they were starving.
The six children were eventually taken to the Riverside University Hospital System (RUHS) and the seven adult children were moved to Corona Regional Medical Centre, according to reports.
The parents were detained under violations of torture and child endangerment.
Their bail was set at $9m (£6.5m) each.
In a statement, police said: “Deputies located what they believed to be 12 children inside the house, but were shocked to discover that seven of them were actually adults.
“The victims appeared to be malnourished and very dirty.”
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Police initially thought the 17-year-old girl was about 10-years-old.
Neighbours said the family was quiet, but they knew it was large. However, they never saw the younger children and they were “suspicious” of the situation.