The body of an 18-year-old woman has been discovered more than a week after she disappeared while hiking in a remote area of New South Wales in Australia.

Lily Hooper’s body was found in bushland in the Southern Highlands, police said in a statement.

While it was “yet to be formally identified”, a spokesperson for the NSW police said, “the body is believed to be that of the 18-year-old woman”.

The discovery was made possible by a multi-agency search operation in the Nattai National Park, roughly 90km southwest of Sydney.

The NSW police said on Thursday that a “hiker” had been located during the search in the rugged mountainous area. The circumstances surrounding the woman’s death were yet to be established.

“I have got some terrible news,” NSW premier Chris Minns told a parliamentary hearing on Thursday.

“It seems as if the earlier advice was wrong.”

Just minutes earlier, Mr Minns had said the woman had been “found alive”.

“Lily’s body has been found. She’d been found deceased. This is obviously devastating, and I’m profoundly sad for her family and for all those concerned. I apologise.”

Hooper set out from her home southwest of Sydney on 12 August for a hike through the Nattai park.

When her vehicle was found abandoned close to the Bonnum Pic Walking Trail, authorities began an extensive search involving around 100 Australian Defence Force personnel and covering dense bush, steep slopes, and cliff edges.

Police also used a thermal-equipped helicopter and telecommunications information to help determine the woman’s movements. Her family stayed at the search command post as the operation continued.

Her body was finally located in the dense bushland at about 11.30am local time on Thursday. Police had been told she was an experienced hiker.

Ms Hooper’s family were initially told she had been found alive.

Assistant police commissioner Joseph Cassar did not directly explain why the parents were initially told she was alive, but said there was “no playbook for communication”.

“I can tell you the police that was in charge at the time that spoke to Lily’s mum and dad certainly hoped for a more positive outcome,” he said. “If we are able to provide them more detailed information on that first report, I can tell you that would have been the case.”

“But unfortunately, it did take that small period of time for us to give them an update.”

Hooper’s family believed she was alive for about “eight to 10 minutes”, police said.

“It’s an eight-day coordinated search, we’re talking about hundreds of volunteer people that are trained in searching, we’re talking about thick dense terrain, we’re talking about processes that we’ve adopted to engage family members to keep them informed throughout every step of the way,” Mr Cassar said.

“So when we talk about a very short window in information being provided, no I don’t believe we’ve jumped the gun.”

Australian prime minister Anthony Albanese described Hooper’s death as an “unspeakable tragedy”.

“Lily Hooper had so much more to offer the world,” Mr Albanese said. “Her passing, I have no doubt, will be felt very deeply across the southern highlands, among her family, her friends, and indeed right across the nation.”

NSW opposition leader Kellie Sloane said in a statement that Hooper’s death was “devastating”.

“So many people had been hoping for Lily’s safe return and today’s news will be difficult and deeply felt,” she said.