The cellar where Austria's Josef Fritzl held his daughter for 24 years and fathered seven of her children is being filled with cement.

Walter Anboeck, who is in charge of Fritzl's estate, said Thursday that work has started and the basement should be filled with concrete in about two weeks.

Fritzl's daughter Elisabeth disappeared from her town of Amstetten, Austria, in 1984 at age 18. In 2008, she re-emerged from the dungeon-like basement chamber where her father had kept her captive.

He had raped her thousands of times. She bore him seven children, and one of them died in captivity after Josef Fritzl refused to allow medical treatment.

Josef Fritzl was sentenced to life in a prison psychiatric ward in March 2009. Elisabeth Fritzl and her children were given new identities.