Austrian police are continuing to question an elderly man who admitted holding his daughter in a cellar for 24 years and fathering her seven children.
Police said Josef Fritzl also admitted burning the body of a baby who died at the house in Amstetten, Lower Austria.
Mr Fritzl, 73, remains in custody. His daughter, now 42, and her six surviving children have been taken into care.
A lawyer for the victims said the case showed no sign of institutional failure on behalf of the Austrian authorities.
"Up until now there is no sign that there was any mistake by officials," the lawyer, Christoph Herbst, was quoted as saying by the Austrian Press Agency (APA).
Pictures of Josef Fritzl's house and cellar
"If there had been such a mistake we would obviously have to talk about it."
However, Austrian media are questioning how such grave crimes went undetected for so long.
Lured into cellar
Photos of Mr Fritzl's basement show a concealed network of tiny windowless chambers which were soundproofed.
Prosecutors say Mr Fritzl is expected to be taken into protective custody after appearing before a magistrate.
His daughter, Elisabeth, disappeared aged 18 on 28 August 1984 when, according to her testimony to police, her father lured her into the cellar, drugging and handcuffing her before locking her up.
She is reported to have been made to write a letter which made it look as if she had run away from Amstetten, a small town about 130km (80 miles) west of Vienna.
The head of the criminal affairs bureau in Lower Austria, Franz Polzer, said Mr Fritzl had admitted sexually abusing his daughter repeatedly during the time he imprisoned her.
Mr Polzer said Mr Fritzl told investigators Elisabeth had given birth to seven children, including twins in 1996, but one died shortly after being born and that he had thrown the body into an incinerator in the building.
The surviving children are now aged between five and 19 years.
Wife 'unaware'
The cellar rooms, covering an area of approximately 60 sq m (650 sq ft), were equipped for sleeping and cooking, and with sanitary facilities.
A reinforced concrete door was built into the wall that separated the "dungeon" from the house and electronically locked - the code known only to the suspect, who provided his captives with food and necessities, police said.
Three of the children were kept in the cellar with their mother and had never seen daylight, police told a news conference.
The other three children were adopted or fostered by the suspect, after he forced Elisabeth to write a letter saying she could not look after the baby, according to police.
His wife, Rosemarie, with whom he had seven of their own children, appears to have been unaware of the alleged crimes, police said.
The security chief for Lower Austria, Franz Prucher, said he had been down into the cellar where it was easy to understand how the abuse was not discovered.
"The cellar is very deep," he said. "There you can cry and nobody will hear, nobody. There you can cry as loud as you can, you can hear nothing."
The alleged abuse and Mr Fritzl's apparent double life came to light when the eldest of the children in the cellar, 19-year-old Kerstin, became seriously ill earlier this month and had to be taken to hospital.
Kerstin is said to be in a coma in hospital.
The media were told the other children who had been kept in the cellar were in surprising physical health, but very pale.
The BBC's Bethany Bell says the case is reminiscent of that of Natascha Kampusch, the Austrian teenager held captive in a cellar in a house in a Vienna suburb for eight years, who ran to freedom in 2006.
Our correspondent says the people of Amstetten are in a state of shock over the events in their town, compounded by the sudden worldwide media interest.
Source: MJFM
