An Australian bomb squad safely freed a teenager who was trapped inside a wealthy Sydney mansion near a suspicious device Wednesday, ending a 10-hour ordeal.

Police still don't know whether the device is an explosive, but are looking for a person who police believe placed the device in the woman's home, New South Wales State Police Assistant Commissioner Mark Murdoch said.

"We want to get our hands on who's done this," Murdoch told reporters.

The incident began at 2:30 p.m. after police were called to the home on Burrawong Avenue, a wealthy suburb of Mosman, by the 18-year-old woman.

Saying the incident was "very sensitive," Murdoch kept their cards close to their chests, refusing to confirm reports the device had been tethered to her body.

According to a senior police officer, the device was an unusual "collar bomb," which has never been seen before in Australia.

It has been speculated that an intruder wearing a balaclava entered the house, attached the explosives to the girl and left a ransom note attached to her neck.

Murdoch said the teen was doing well and was with her parents.

"She's good - she's been kept in a very uncomfortable position," he said. "She has been and will be uncomfortable for a little while to come."

Murdoch said it was "far too early to say" whether the device had been placed in the teen's home as part of an extortion attempt, and refused to comment on a report that a note had been left alongside the device.