FRANKFURT  Austrian police arrested a 73-year-old man who they say kept his daughter locked in a cellar for 24 years and fathered seven children with her, three of whom never emerged into daylight from their prison until now.

The woman, identified by the police as Elisabeth F., was released by her father, Josef F., after her eldest daughter, 19, became ill and was taken to a hospital. Doctors had appealed for her mother to come forward to share details of her medical history. The authorities said she was still in serious condition.

The police referred to the family name by initial only as is standard procedure in criminal cases in Austria.

In its macabre details, the case carries echoes of the kidnapping of Natascha Kampusch, an Austrian schoolgirl who was held in a windowless basement cell for eight years before escaping in August 2006. This latest case, which unfolded in a nondescript, three-story apartment house in Amstetten, a town 80 miles west of Vienna, is, if possible, even harder to comprehend.