Sydney (CNN) -- The suspected bomb that triggered a 10-hour drama in Australia has turned out to be an elaborate hoax, police said Thursday.
They confirmed that no explosives were found at the site of the drama -- a home in an affluent suburb of Sydney.
"A very, very elaborate hoax, as it turned out," New South Wales Police Assistant Commissioner Mark Murdoch told Seven Network. "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."
But police continued to investigate who was behind the hoax and they continued to look for an intruder as described by the woman who said that intruder attached a device to her.
Details about the incident remained sketchy.
Madeleine Pulver, 18, told police that a man wearing a disguise entered her home Wednesday afternoon and attached a suspicious device to her. "We are unsure how the person we are looking for, the offender, gained entry to the premises, but certainly he managed to take Madeleine by surprise," police said.
Pulver was taken to a local hospital but has since been released and reunited with her parents, according to CNN affiliate ABC Australia. Police said they felt that a medical assessment was necessary since she was kept in an extremely uncomfortable position for many hours, Assistant Commissioner Mark Murdoch said.
The investigation into the incident will be led by the State Crime Command's Robbery and Serious Crime Squad, according to a statement on the New South Wales Police Department's website. That unit deals with extortion, according to ABC Australia.
Australian media are reporting that Pulver's father works for an international software company, and that police are investigating the possibility that it was an elaborate extortion attempt.
"We do not know the motive, but that will be the focus of the investigation," Murdoch said.
"This is an unusual incident for New South Wales and indeed Australia," Murdoch told ABC Australia earlier. "I'm not aware of anything like this happening in the country before, and I think that is what's made it so unusual ... Certainly the family are at a loss to explain this. But you wouldn't expect someone would go to this much trouble if there wasn't a motive behind it."
Murdoch said at a news conference earlier, "The safety of the young lady was always our first priority, and I am pleased to say we have achieved this. Her parents, in particular, are extremely relieved.
The situation, in the wealthy suburb of Mosman, was resolved soon after midnight Wednesday.
Officers had been contact with explosives experts in Europe and the United Kingdom during the operation, according to Murdoch.
Nearby homes were evacuated and neighboring streets closed off by police. Footage from the scene showed numerous emergency response personnel and vehicles stationed along the street.
Australian news reporter and Mosman resident Dave Kirwan told CNN late Wednesday that the police had not given much detail but had said the girl was not able to leave the vicinity of the device, suggesting she was be attached to it.
Kirwan said he had caught a glimpse of the girl's parents outside the property, looking distraught.
Police told reporters there were four people inside with the girl and they were trying to keep her calm, he said.
About eight hours into the situation, some people living in the immediate vicinity were told they would not be able to go home for the night, he said.
Mosman is a very wealthy suburb on Sydney Harbor, where many well-connected people, sports stars and celebrities live, Kirwan added.
"This kind of thing doesn't really happen here," he said. "Everyone is really, really scared."
Many residents had locked themselves into their homes when the alarm was first raised, he said, fearing that they might also be in danger.
CNN's Hugh Williams, Laura Smith-Spark, Phil Han and Amir Ahmed contributed to this report.