Australian police say a device attached to a teenager that took 10 hours to remove was part of an elaborate hoax. Madeleine Pulver, 18, was at home in Sydney when an intruder apparently entered and placed a suspected explosive device round her neck. Police said the intruder left behind a note that could provide leads for their investigation. They are reportedly looking into the possibility that the hoax was part of an extortion attempt. "A very, very elaborate hoax as it turned out," was how New South Wales Police Assistant Commissioner Mark Murdoch put it to journalists. "But it was made and certainly gave the appearance of a legitimate improvised explosive device. We had to treat it seriously until we could prove otherwise and that's exactly what we did and that's why it took so long." The device was attached "by a chain or something similar," he said. "The offender went to a lot of trouble for a particular reason, but what that reason was, police are still working to determine," Mr Murdoch added.