AMSTETTEN, Astria — The secrets of Austria’s “house of horrors” were disclosed Monday as a retired engineer confessed to keeping his daughter locked up in a cellar for 24 years and fathering seven children by her.

Josef Fritzl, 73, admitted he had forced his daughter Elisabeth into the cellar in 1984, when she was 19, and kept her there together with three of her children who had spent their entire lives in the bunker until they were released last week.

In what one Austrian newspaper described as “the worst crime of all time,” Mr. Fritzl kept his captives under control by telling them they would die if anything happened to him.

He hoodwinked his entire family and the local authorities into believing Elisabeth had run away.

The full extent of the ordeal suffered by Elisabeth and three of her children was illustrated yesterday when police released photographs of some of the rooms inside the dungeon-like cellar in Amstetten. The entrance was via a 3-foot-by-2-foot steel door, concealed behind a cupboard in an underground workshop. It could only be opened from the outside or via a remote control Mr. Fritzl kept on him.

Inside are five tiny rooms, each 5 feet 6 inches high, including two bedrooms, a bathroom, and a storeroom with rubber-lined walls in which one of the children, who is epileptic, would be taken whenever he had a fit.

Police would not say whether the padded room was used for more sinister purposes, but Colonel Franz Polzer, leading the investigation, said the dungeon “contained a room which made it possible for him to continue his abuse over many years.” The cellar was originally 3 feet high, police said, but Mr. Fritzl, who reportedly served a prison sentence in the 1960s for a previous sex offence, enlarged it and added more rooms, with electricity and running water, over the years.

Police are investigating how Mr. Fritzl was able to buy food and clothing for the four prisoners without his 66-year-old wife, Rosemarie, finding out. Colonel Polzer said: “His wife didn’t ever know what was going on because in this house, he was very authoritarian, and whatever he said was adhered to.”

Elisabeth Fritzl gave birth to her first child, Kerstin, 19 years ago. Kerstin spent her entire life in the cellar together with Stefan, 18, and Felix, 5. They saw daylight for the first time when Fritzl decided to disclose their whereabouts to police after taking Kerstin to the hospital with an illness which has left her in a coma.

“It was a terrible scene down there,” said one police source. “They had difficulty adjusting to the sunlight. They had never seen it.”

Until then, their only connection to the outside world had been a television. Felix was fascinated by cars he saw on TV and, the source said: “As he was driven to the hospital he was very excited to be driven in one for the first time.”

Mr. Fritzl raised three other children – Lisa, 16, Monica, 14, and Alexander, 11 – in his house, after claiming Elisabeth had left them on the doorstep as babies with notes he had, in reality, forced her to write, asking him to look after them.

A seventh child, Monica’s twin brother, died after three days. His body was burned by Mr. Fritzl.

Elisabeth and her children are all in the hospital, where their mental and physical health is being assessed. Police said Ms. Fritzl was in “a serious condition” and was “a broken woman.”