The body of missing 18-year-old bushwalker Lily Hooper has been found in a remote New South Wales national park more than a week after she set out on her hike.

NSW police said in a statement: “The body of a woman has been located in bushland following the search for a missing bushwalker in the Southern Highlands.”

A police spokesperson said “while yet to be formally identified, the body is believed to be that of the 18-year-old woman”. They said a report would be prepared for the coroner.

Earlier on Thursday, NSW police said a “hiker” had been found after the multi-agency search in the rugged terrain of Nattai national park, about 90km south-west of Sydney.

“I’ve got some terrible news,” the NSW premier, Chris Minns, told a parliamentary hearing on Thursday. Just minutes earlier, Minns had said Lily had been “found alive”.

“I apologise … it seems as if the earlier advice was wrong,” he said.

“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.”

Minns said in a statement he received incorrect advice and “genuinely believed” he was sharing good news.

“My deepest condolences are with Lily’s family,” the premier said. “I am profoundly sorry to think that anything I said may have added to their heartbreak at an already devastating time.”

Minns had initially told a parliamentary hearing that Hooper was “found in the bush with half a bottle of water with her”.

Hooper left her Sydney home on Wednesday 12 August for the hike. Initial police inquiries suggested she reached the summit of Bonnum Pic mountain mid-morning on Wednesday, having sent messages from the trail earlier that day.

She was reported missing when she did not return home that evening. Her car was located by emergency services near the trail head on Wanganderry Road at High Range on Wednesday night.

More than 100 ADF personnel had joined the search operation in the past 24 hours. The army personnel joined people from PolAir, NSW Police Rescue, SES, RFS, Fire and Rescue NSW, and National Parks and Wildlife Service.

Volunteers on the ground include Hooper’s family, family and Volunteer Rescue Association crews mobilised from as far north as Cessnock.

On Monday, police said the search was focused on the lower sections of the Bonnum Pic walking trail.

The NSW police Ch Insp Brendan Bernie said earlier this week: “It’s quite dense with the bushland and there’s a dense tree canopy which also hinders our aerial searching.”

Police were uncertain of what supplies Hooper had with her.

“We’re hopefully relying on Lily’s experience to get her through this ordeal and can locate her safely,” Bernie said on Monday.

Poor weather over the weekend had hampered search operations in the already complex terrain.

Angus Taylor, the opposition leader and the local MP for the electorate where the Hooper family live, paid tribute to her in parliament on Wednesday.

“Any parent who reads this news will hug their children tighter tonight,” he said.

“When they do, they will spare a thought and a prayer for Lily’s mother, father, and family who can’t do the same. We grieve for their most terrible loss.”

The prime minister, Anthony Albanese, said Hooper’s death was an “unspeakable tragedy”.

“Lily Hooper had so much more to offer the world,” 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.”