Austrian police have appealed to about 100 former lodgers in the house where a pensioner kept his daughter prisoner in a dungeon for 24 years to come forward in the hope that they can throw light on the crime and how Josef Fritzl was able to carry it out apparently unnoticed.
Frank Polzer, the regional police officer leading the investigation, said that those who had rented accommodation from Fritzl in his imposing grey house on Ybb street were vital to piecing together clues of the worst known incident of its kind.
"In the past 24 years around 100 people have lived in the house," Polzer said. "We want to talk to all of them - possibly one of them observed something that at the time didn't seem so important but could be of relevance knowing what we do today."
One former resident, Alfred Dubanovsky, came forward yesterday to talk of how he had seen another man enter the dungeon. Dubanovsky, a petrol pump attendant who lodged in the house for 12 years, said he believed the man had been a plumber who came to help Fritzl install a toilet.
He added that Fritzl had once told him: "One day my house will go down in history."
A sister-in-law of the 74-year-old yesterday became the first family member to break their silence. Christine R, 56, sister of Fritzl's 68-year-old wife, Rosemarie, told the Austrian newspaper Österreich that her brother-in-law was a "despot".
"I always hated him," she said, referring to him by his nickname, Sepp.
"He drilled his kids and when he entered a room, silence fell over everyone immediately - even when they were in the middle of playing a game. You could sense their constant fear of being punished."
She said she saw his tyrannical behaviour towards his seven elder children - now aged between 37 and 51 - as the main reason why most of them had married young. "The only chance for the children to escape this atmosphere was to marry," she said. "And that's what they all did as soon as they were old enough."
She described how he expected his wife to play a subservient role to him from the start of their married life. "When Rosemarie married Sepp she was 17, and had no professional qualification, so she was always dependent on him - and for 51 years he exploited that."
He frequently "put her down" and told perverse jokes in her presence, she said.
The most difficult time for the family came in 1967 when Fritzl was convicted of raping a young woman in Linz, a crime for which he received an 18-month prison sentence. "I was 16 at the time and I found the offence simply disgusting - all the more so seeing as he already had four children with my sister," she said.
Christine said that all the family knew that Fritzl withdrew for hours to his "cellar" at the back of the garden - the site of his workshop and office, and of the well-hidden entrance to the dungeon.
"Every day at 9am Sepp would go to the cellar, supposedly to produce blueprints for machines he had been commissioned to build." Often he even stayed there overnight, she said, telling his wife under no circumstances was he to be disturbed. "Rosi was not even allowed to bring him a cup of coffee."
The woman who was raped by Fritzl in 1967 also came forward yesterday, saying she had received a shock on seeing his picture. "I recognised him immediately," she said. "I will never forget those eyes." Fritzl had raped her in her bed at knifepoint after climbing through the kitchen window of her flat while her husband, a railway worker, was on a night shift.
Police technical experts were yesterday investigating a claim made by Fritzl's 42-year-old daughter, Elisabeth, that her father had threatened to pump her prison with poisonous gas if she and three of her children by him tried to escape. "He apparently told his daughter that in case they tried anything on, gas would flow into the dungeon, which might possibly be an explanation for why the prisoners never ventured to overpower him," said a criminal investigator, Helmut Greiner.
Rosemarie Fritzl also revealed to the police how she believed she had received a call from her daughter in 1994, 10 years after she had believed Elisabeth had fled the family home to join a sect. Police now believe the call in which Elisabeth supposedly asked her parents to look after a baby that she had just left on their doorstep was made from a telephone box by Fritzl who tried to imitate his daughter's voice. Rosemarie later asked how it was that Elisabeth had known their new telephone number.
Three babies were eventually raised by Rosemarie. A letter to her family, dictated by Fritzl and written under duress by Elisabeth late last year, indicated that he was considering ending her captivity by staging her return. In the letter she said she was thinking of coming home. But it now appears that any plans he might have had were overtaken by events. He took his sick 19-year old daughter, Kerstin, out of the dungeon and to the local hospital two weeks ago. Police were called when Fritzl visited the hospital accompanied by Elisabeth. He was subsequently arrested after Elisabeth told officers of her ordeal.
Police said it was only possible to speculate why Fritzl wanted to stage her return. "Perhaps he was aware that he couldn't keep the thing going forever," Polzer said. "Maybe he sensed that his strength was waning."
The cellar children, their mother, grandmother and the three other children who lived "upstairs" were continuing to be cared for by medical professionals in a psychiatric clinic yesterday. They were said by the clinic head, Berthold Kepplinger, to be "devouring" the media coverage of their release on television and in newspapers.
Some Austrian commentators criticised the Austrian chancellor Alfred Gusenbauer's concerns that the dungeon drama would damage the country's image.
"It would make sense to start looking for answers - many of which are slumbering deep within ourselves - instead of reacting in a patriotic knee-jerk way," said an editorial in the Kurier.