Police today appealed to about a hundred people to help them piece together details of a quarter-century of incarceration of an Austrian woman and her children by her father and sexual tormentor.
Investigator Franz Polzer asked for help from all those who had lived in the block in the small town of Amstetten in whose cellar Josef Fritzl imprisoned his daughter Elisabeth in 1984, and then fathered seven children by her.
"I ask if perhaps any one of them may have seen something noteworthy that at the time may have seemed insignificant," Mr Polzer told a news conference.
Incredulity is driving a judicial and public effort to understand how a man could have entombed his daughter under the noses of residents and authorities, and then kept three of the children he fathered with her underground their entire lives.
Austrian and German media reports have shown pictures and video clips of Fritzl contentedly holidaying without family members in Thailand and Cyprus.
Mr Polzer said the cellar, which was sealed off behind a locked sliding concrete door, included separate sleeping, washing and cooking areas, and was equipped with a refrigerator, freezer and washing machine.
"This electrical equipment would have allowed the occupants of the dungeon to have survived for weeks," he said.
Two of the children who had lived in the cellar have now been reunited with three other siblings who were taken in as infants and raised by Josef and his wife Rosemarie.
Yesterday we had a small improvised birthday celebration for the 12-year-old, with a birthday cake," Berthold Kepplinger, medical director of the provincial clinic of Lower Austria, told the same news conference..
The eldest child, aged 19, remains seriously ill in hospital, where she was taken last week - the first time she had left the windowless cellar.
Josef Fritzl, who has admitted incarceration and incest, is now in detention and under investigation on suspicion of rape, incest and coercion. He is also being investigated for murder through neglect of a seventh child, which died shortly after birth, and whose remains he burnt in a furnace.
Fritzl's lawyer, renowned defence attorney Rudolf Mayer, said his client was refusing to answer further questions.
"He has given police a comprehensive statement," Mr Mayer said. "At present there is no need for further questioning ...
"The DNA traces are clear and this would prove the incest. But the rape has not been proven at all, let alone the enslavement and the murder that have been talked about. Nothing has been proven there."
The case comes less than two years after an Austrian teenager, Natascha Kampusch, escaped from the basement where she had been locked up by an abductor for eight years.
Local authorities say they do not blame officials for failing to discover the case earlier. They say those who allowed Fritzl and his wife - who had six other grown-up children of their own - to take in three of Elisabeth's children were acting within the law.
The case spurred Chancellor Alfred Gusenbauer to announce an image campaign to restore Austria's reputation abroad.
"It's not Austria that is the perpetrator. This is an unfathomable criminal case, but also an isolated case," he told journalists in Vienna.
It was also reported today that police were examining a possible connection between the murder of a young woman 22 years ago and Fritzl.
The body of Martina Posch (17) was discovered on the shore of Mondsee lake near Salzburg where Josef Fritzl owned property. She was believed to have been raped.