Austria (Reuters) - A 73-year-old Austrian electrical engineer has confessed to holding his daughter captive in a secret, windowless cellar for 24 years and fathering seven children by her, police said on Monday. The case, centred on a nondescript two-storey building in the small industrial town of Amstetten, bears chilling similarities to that of Austrian Natascha Kampusch who spent eight years locked up in a basement before escaping in 2006. Some parts of the 60 square metre basement in which the family were kept were no more than 1.70 metres (5 ft 6 in) high and officials said the basement even contained a padded cell. "This is an appalling crime. I know of no comparable case in Austria," Franz Prucher, head of security for Lower Austria told a news conference. Elisabeth Fritzl, 42, says her father, Josef Fritzl, lured her into the basement of the block in 1984 and drugged and handcuffed her before imprisoning her. Three of her children, aged 19, 18 and 5, had been locked up in the basement with her since birth and had never seen sunlight, police said, raising worries about their physical and mental state. The younger two were boys, the eldest a girl. The victims are receiving medical treatment, said police. Three other children -- two girls and one boy -- were brought up by Josef and his wife. As well as confessing to locking up his daughter for 24 years and siring the seven children, Fritzl admitted to burning the body of the seventh child in the heating system when it died soon after birth, said Franz Polzer, head of criminal investigations in the state of Lower Austria. Investigators spent the day combing through the cells where the victims had been held captive. Forensic experts in white uniforms and gloves carried out boxes of evidence from the house which is on a busy street with shops. AUTHORITARIAN Fritzl, whom police described as "dynamic, bossy and authoritarian", had hidden the entrance to the cell behind shelves and only he knew the secret code for the reinforced concrete door, said officials. Photographs showed a narrow passageway leading into other rooms which included a cooking area, with children's drawings on the walls, a sleeping area and a small bathroom with a shower. The victims' only sources of information from the outside world were a television and radio. Amstetten, located in rolling hills about 130 km (80 miles) west of Vienna, is an industrial town of about 22,000 people. The case unfolded when the 19-year-old girl became seriously ill and was taken to hospital, prompting doctors to appeal for the girl's mother to come forward to provide more details about her medical history. Fritzl then brought Elisabeth and her remaining two children out of the basement, telling his wife -- who thought their "missing" daughter had chosen to return home, police said. Elisabeth agreed to make a thorough statement to the police after receiving assurances she would have no further contact with her father, who she said abused her from the age of 11. SHAME The case has raised questions about how authorities and neighbours failed to notice anything unusual in the "house of horrors", not least because officials said Fritzl had over the years built extensions to the secret cellar. "The community of Amstetten should drown in shame ... The neighbours are turning a blind eye," the Oesterreich newspaper wrote in an editorial. The daily Der Standard wrote: "The whole country must ask itself what is really, fundamentally going wrong." Polzer said Fritzl had led a "double life" for 24 years. "He deceived us all," he told reporters. "This man, who already had a family with seven children by his wife, had in this cellar seven more children by his own daughter," he said. Another puzzle is how Josef's wife Rosemarie could have remained ignorant. Police have said they believe Rosemarie did not know what happened to her daughter when she disappeared in 1984. It was assumed Elisabeth had left voluntarily when her parents received a letter from her saying they should not search for her. After Elisabeth disappeared, Fritzl said Elisabeth had joined a sect and that she had left the children on the doorstep. He forced Elisabeth to handwrite letters to prove his claims, said the police. Psychiatrist Max Friedrich, who treated Kampusch, said the children were undergoing tests in hospital, in particular for problems with their eyes and skin due to the lack of daylight and that they would need trauma therapy. "And socially ... the (children) could not develop any sort of sense of community which they would get from going to school or playgroup," Friedrich told Reuters. By contrast, the children raised by their grandparents were integrated into the community, said officials, noting they were members of the police sports club and voluntary fire brigade. Kampusch, who spent her teenage years in captivity, offered to help the victims and told ORF radio she might talk to them. "I can imagine that it is very difficult both for the mother of the children as well as for the wife of the perpetrator to get through this," she said.