An Austrian engineer has confessed to fathering seven children by raping his own daughter and keeping them captive in the cellar, Austrian police said today.

During the 24 years that Josef F kept his daughter Elisabeth locked up in a windowless cellar underneath the house where he lived an outwardly blameless life with his wife Rosemarie, the 73-year-old is said to have fathered and then acted as midwife at the birth of children now 19, 18, 16, 14, 11, and 5, Austrian police have revealed.

A seventh child - a twin boy - was said by police to have died three days after his birth and his body to have been burned in the large, well-kept gardens of the grey, concrete villa in Ybbs Street in the eastern town of Amstettin.

Mr F, who was arrested on Saturday night at the hospital where Kerstin has been lying in a coma for over a week, was this morning said to have begun to speak to police for the first time. Until last night he had told them little more than the code to the hidden electronic trapdoor to the windowless cellars where the secret family was kept imprisoned.

“He has now said that he locked up his daughter for 24 years and that he alone fathered her seven children and that he locked them up in the cellar,” said Colonel Franz Polzer, head of the criminal investigations unit in the province of Lower Austria.

Prosecutors said a little later however that Mr F had confessed only to imprisoning his daughter and her children, and not to incest.

Josef F “has admitted building the dungeon and to holding his daughter and three children there. But he has not admitted incest,” said Gerhard Sedlacek, a spokesman for Austrian prosecutors.

Mr F has been transferred to court and is expected to appear before an investigating magistrate this evening. DNA test results that will determine whether he did indeed father his daughter Elisabeth's children, as she has claimed, are not expected for two days.

Police have spent the night exploring the network of rooms where they say Elisabeth was first imprisoned on August 28 1984, aged 19, after being drugged and handcuffed by her father. The tiny entrance was concealed in a workshop in a public part of the cellar.

"There was a shelf with plenty of cans and containers, and behind the shelf was a door made of reinforced concrete, secured electronically and running on steel rails, and only the suspect knew the code," said Heinz Lenze, a local police official.

Once inside the dungeon, police reported, they found all the passages extremely narrow, the ceiling is no higher than 5ft 6ins (170cm) and the floors uneven. They have found a makeshift shower room, cooking rings for the secret family to heat food, and a room lined entirely in rubber whose use is unknown.

Mr F, a retired engineer who used to work for the construction company Zehnter, was said by police to have been continuously renovating and extending the hidden cellar. Detectives say they have not ruled out finding further secret rooms underneath the sprawling villa.

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