AMSTETTEN , Austria -LRB- CNN -RRB- -- Austrian police believe a 73-year-old man held his daughter captive in his cellar for the past two decades and fathered at least six children with her , according to police and state-run news reports Sunday . The woman , identified as 42-year-old Elisabeth F. , has been missing since 1984 , when she was 18 years old , police said at a news conference . The situation came to light earlier this month after her daughter -- a 19-year-old woman , identified as Kristen F. -- was hospitalized in Amstetten after falling unconscious , according to police . She was admitted to a hospital in Amstetten , outside Vienna , by her grandfather with a note from her biological mother requesting help . Amstetten is a rural town about 150 km -LRB- 93 miles -RRB- west of Vienna . But police said a DNA test later revealed her grandfather , Josef F. , was also her father , according to ORF , Austria 's state-run news agency . That sparked a police investigation , which revealed that Josef F. may have fathered at least six children with his daughter , forcing her and three of the surviving children to live in the cellar of his house , according to ORF 's Peter Schmitzberger . The children are now between 5 and 19 years old . Police are awaiting DNA tests to verify their relationship to Josef F. , who faces arrest for `` severe crimes against family members , '' according to police . So far , he has not given a statement to police . Police spokesman Franz Polzer told ORF that the 73-year-old has led police to several hidden rooms in his cellar accessible only by an electronic passcode that he provided to police . Watch a report on the discovery '' On Sunday , police searched the hidden rooms where Josef F. admitted he kept his daughter and their children , Polzer told ORF . The rooms included sleeping quarters , a kitchen and a bathroom , which Josef F. told police he built , Polzer said . Neighbors told ORF they were shocked to hear the news , and had no indication such horrors were taking place in their town . `` One ca n't imagine how it could happen , how nobody could realize anything of what was going on in the cellar of this house , '' Schmitzberger told CNN . `` It 's quite unimaginable . '' Acting on `` a confidential tip , '' Amstetten police apprehended Josef F. and Elisabeth F. on Saturday near the hospital for questioning , according to a police statement . Once police assured the daughter that she would never have contact with her father again , `` she was able to tell the whole story , '' Schmitzberger said . Josef F. lived upstairs with his wife , Rosemarie F. , who police said had no idea about her husband 's other family living in the cellar . Josef F. and Rosemarie F. had adopted three of the children that he had with his daughter , according to police . He told his wife that his missing daughter had dropped the unwanted children off at the house because she could not take care of them , police said . The other three children -- Kerstin , 19 ; Stefan , 18 ; and Felix , 5 -- remained locked in the basement with their mother , according to police . None had seen the light of day during their entire time in captivity , police said . After she was detained Saturday , Elisabeth F. gave police a `` psychologically and physically disturbed impression , '' police said in a statement . She told them her story after she was assured her children would be protected from further harm . She said her father began sexually abusing her at age 11 . On August 8 , 1984 -- weeks before she was reported missing -- her father enticed her into the basement , where he drugged her , put her in handcuffs and locked her in a room , she told police . For the next 24 years , she was constantly raped by her father , resulting in the six surviving children , she said , according to the police statement . She told police she gave birth to twins in 1996 , but one of the babies died a few days later as a result of neglect , and Josef F. removed the infant 's body and burned it . She told police that only her father supplied her and her children with food and clothing , and that she did not think his wife knew anything about their situation . When Kerstin fell ill earlier this month , Josef F. apparently told his wife and the hospital that his `` missing '' daughter had dropped off the sick girl on his doorstep . In an effort to find out what might be ailing 19-year-old Kerstin , the hospital asked the media to put out a bulletin requesting any information about the girl or her missing mother , attorney general Gerhard Sedlacek told NTV . Sometime later , Josef F. brought Elisabeth F. out of the cellar , telling his wife that she had returned home with her two children after a 24-year absence , police said . He took Elisabeth F. to the hospital to talk with doctors about Kerstin 's condition , and at that point , authorities became aware of her situation , Sedlacek said . E-mail to a friend CNN 's Ben Brumfield contributed to this report .