Fritzl Again.

Former tenant Dubanovsky claims he saw one of Fritz's sons enter the cellar where Fritz's daughter and her children were held captive.

Alfred Dubanowsky said he rented a ground-floor apartment at Josef Fritzl's home from 1995 through 2007. He said there was a verbal agreement between Fritzl and the house's tenants that they were not to enter the cellar or the garden or photograph the premises or they would be kicked out.

Police said Monday that Fritzl also made clear to his wife and children that they were not allowed to go into the basement.

Fritzl has confessed to keeping his daughter Elisabeth in the basement for more than two decades, where he repeatedly raped her and fathered seven children with her -- six of whom survived, police say.

Dubanowsky said he saw Fritzl's son, also named Josef Fritzl, enter the cellar. He also saw the elder Fritzl enter the basement frequently at night.

Once when he asked to talk to the younger Fritzl, the older man told him his son was working and "not to distract him," Dubanowsky told CNN's Frederik Pleitgen.