The Austrian court that deals with the case of Josef Fritzl decided that he be kept in custody for another month, said a court spokesman, according to Reuters. The ruling will be re-evaluated in a month.

Fritzl’s lawyer, Rudolf Mayer, didn’t object to anything at a 15 minutes closed hearing, prosecution spokesman Gerhard Sedlacek told reporters. He also said that it hadn’t been decided when prosecutors would question Fritzl again.

He is held in a prison in the Lower Austria regional capital of St Poelten since his arrest at the end of April when police discovered that he had been keeping his daughter, Elisabeth, in his basement and fathering seven children with her, one of which died shortly after birth. She has been held there for 24 years, after Fritzl told his wife that she had run away from home to join a cult.

Prosecutors are investigating Fritzl for rape, incest, coercion and the death of the baby, though he has not been charged. Police say he has admitted incarceration and incest.

Franz Polzer, the head of the police investigation told on Friday that the house above the cellar, in the small town of Amstetten was being carefully examined.

“We have been using sniffer dogs and ground radar in order not to have to dig up the whole area,” he said, according to Reuters.

Fritzl said in an interview relayed via his lawyer this week that he became addicted to incest with his daughter.

“My drive to have sex with Elisabeth grew stronger and stronger. I knew Elisabeth didn't want me to do what I did to her. I knew that I was hurting her. ... It was like an addiction ... In reality, I wanted children with her,” said Fritzl.

Elisabeth and five of her children are in care with the Austrian authorities at a psychiatric clinic.