VIENNA -- Doctors in Austria have started attempts to revive the 19-year old daughter of Josef Fitzl from her artificially-induced coma, the hospital treating her said Tuesday.

Kerstin Fritzl, the offspring of Josef's incestuous relationship with his daughter Elisabeth, spent her entire life imprisoned in the family cellar in Amstetten, 100 kilometers (60 miles) west of Vienna.

It was only when she was rushed to hospital unconscious on April 19 that Frizl's horrific catalogue of incest and imprisonment came to light.

Kerstin was placed in a coma in intensive care by doctors to allow her vital functions to stabilize.

The process of reducing her medication began Tuesday, the local hospital authority said in a statement, but it could still be a while before she woke up, said spokesman Klaus Schwertner.

Kerstin is the eldest of seven children born to Austrian incest victim Elisabeth Fritzl, now 42, during the 24 years she was sexually abused and imprisoned in a windowless underground cell by her father, Josef.

It was Kerstin's admission to hospital that brought the entire case to light.

The young woman and two of her brothers, aged 18 and five, had until then spent their entire lives in the cellar with their mother, never seeing sunlight.

Three other children born from the incest were brought to live with Josef Fritzl and his wife, while a seventh child died shortly after birth.

Kerstin's mother and siblings are currently being treated at a nearby psychiatric clinic.