London, May 6 : Dungeon dad Josef Fritzl's daughter Elisabeth might not be his only sex slave in the dingy cellar of his house, for new reports have emerged that his granddaughter Kerstin could also be a victim of his monstrous deeds.
According to police, Fritzl targeted Kerstin, his eldest child by caged Elisabeth, after losing interest in her grey-haired mother.
However, they have not been able to quiz the 19-year-old because she is in a coma, fighting for her life in hospital with organ failure, reports The Sun.
Police believe that Fritzl, 73, was bored with 42-year-old Elisabeth, whose looks had been destroyed by 24 dark and violent years locked up under his home in Amstetten, Austria.
Albert Reiter, the doctor in charge of Kerstin's care, said that though she remained crucially ill, she had improved slightly.
He added: "She is in a grave condition and it's impossible to interview her because she is unconscious. We have to wait for a later time to make such investigations. Her condition has improved in the last few days."
Police also revealed that Elisabeth and her children were locked inside a 35-metre square inner dungeon, which could only be reached through eight locked doors.
According to Austrian police, Fritzl imprisoned Elisabeth, in a soundproof, windowless dungeon in his basement for 24 years, where he fathered seven children by her.