Police last night entered the homemade dungeon where a 73-year-old engineer allegedly held his daughter captive for almost a quarter of a century, sexually abusing her and fathering up to seven children.

Behind a hidden door they discovered a complex of small windowless rooms, less than six feet high, where Ms F claims that she was kept imprisoned with three of her children.

Ms F, 42, effectively disappeared in 1984. Since then no passport, driving licence or other official document has been issued in her name. There are no photographs of her since she was at school.

Ms F claims that she was seized, drugged and handcuffed by her father soon after her 19th birthday and locked in the basement of their three-storey home in Amstetten, a small town in eastern Austria. She says she had been sexually abused since the age of 11.

The basement was connected to the house by a hidden door and protected by an elaborate electrical locking mechanism to which only Mr F knew the code. Because he had been an electrical engineer and had access to explosives, police feared booby traps, but they gained entry last night after Mr F, in custody, disclosed the code.

The rooms that they encountered contained sanitary facilities and cooking equipment, and one was described as a padded cell.

The Austrian state prosecutor’s office said that Ms F’s claims were credible and that DNA tests were being conducted to see whether Mr F was indeed the father of her children.

“She had been abused continuously during the 24-year imprisonment,” said a police statement, summarising the testimony of Ms F. “This led to six children.”

Police said she was “greatly disturbed” and agreed to talk only after receiving assurances that her children would be cared for and that she would no longer have to see her father.

A seventh child was born but died three days later. The body of the baby was later allegedly burnt in the garden by her father. The surviving children, three boys and three girls, are aged between 5 and 20 and all are being cared for by police psychologists.

Police found out about, and freed, Ms F after one of her daughters, Child, 19, was taken to hospital eight days ago. She was one of three children living in the dungeon.

All three were fed and clothed by Mr F but they were not allowed to go to school. According to her testimony, Ms F had to teach all three – the others were Child, 5, and Child, 18 – to speak, read and write. Her father passed clothing and food through a hatch.

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