London, May 11 (ANI): Rosemarie, the wife of sex beast Josef Fritzl, is to be questioned again by police to determine whether she knew about his secret life in the cellar.

Detectives are to conduct a forensic search of the upper floors of the "house of horrors" where Fritzl, 73, lived with his 68-year-old wife, while their daughter Elisabeth, whom he raped for 24 years and fathered 7 kids with her, was locked in the basement.

"We think Fritzl acted alone but cannot exclude the possibility that someone else was aware of what was going on downstairs," Times Online quoted Frank Polzer, the chief investigator, as saying. Fritzl last week urged his wife to visit him in jail. It is not known if she intends to do so.

Her claim to have known nothing about her daughter's ordeal has raised eyebrows, as has the collective blindness of Amstetten, a town 75 miles west of Vienna, to what was unfolding beneath one of its main streets. (ANI)