Law enforcement officials told the celebrity gossip website surveillance footage from Cyrus' home and the homes of neighbors don't appear to show anyone suspicious leaving or entering the house last month when her home was robbed.
There were no signs of forced entry.
The sources said police are questioning a number of workers who had access to the house at the time of the theft.
Cyrus told the New York Times her recent headline-grabbing performances and interviews have all been an act.
"I went from people just thinking I was, like, a baby to people thinking I'm this, like, sex freak that really just pops molly and does lines all day," she said. "It's like, 'Has anyone ever heard of rock 'n' roll?' There's a sex scene in pretty much every single movie, and they go, 'Well, that's a character.' I don't really dress as a teddy bear and, like, twerk on Robin Thicke, you know?"