Amstetten, Austria (AP) Police say the Austrian incest-imprisonment suspect planned to build his secret cell as early as 1978, when his daughter was just 12 years old.
Investigators also say a total of eight doors secured the underground warren of windowless rooms where Josef Fritzl held his daughter captive for 24 years and fathered seven children with her.
Prosecutors told reporters today in the town of Amstetten, west of Vienna, that they will have their first meeting with Fritzl this Wednesday or Thursday.
Officials at a psychiatric clinic say Fritzl's wife, the daughter he allegedly imprisoned and raped, and the children born of the illicit relationship are learning how to live together.
The 73-year-old suspect has not yet been charged, but his lawyer has said he is preparing an insanity defense.