AMSTETTEN, Austria (CNN) -- 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 after falling unconscious, according to police.

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.

The children are now between the ages of 5 and 19 years old.