Pheobe Bishop, 17, was last seen near Queensland's Bundaberg airport about 8.30am on May 15 after booking a trip to Western Australia.
Searching continued on Saturday at Good Night Scrub National Park, about an hour's drive from the airport, as part of expanded efforts involving homicide detectives and divers.
"The search of the ... national park area is crucial to the police investigation," Queensland Police Senior Constable Matthew Baker told reporters.
Police said they were relying heavily on leads from the public to solve Pheobe's disappearance, encouraging anyone with information "big or small" to come forward.
CCTV footage indicated the 17-year-old never entered the airport for the planned trip to visit a friend.
Her family released a statement on Saturday, describing her as strong-willed and someone who followed her own beat and loved music.
"I've always called her my 'wild gypsy banshee'," the statement said.
"You can't tame Phee's spirit, empathy or fight for life. She is sassy, feisty and loves harder than anyone I've ever (met).
"Phee loves beyond comprehension and is loyal to her siblings."
A property at Gin Gin, where Pheobe lived with two other people, was earlier declared a crime scene.
A grey Hyundai ix35 believed to have been used to take her to the airport has been seized by police.
Her family has appealed for anyone who might have heard from Pheobe or knew anything about her whereabouts to come forward.
"She is an essential part of our lives and we need her home. We need to hear her music, feel her hugs and hear her voice," they said.
"Pheobe would never not touch base with the people she loves. She would never go this long without contacting someone or anyone."
Her mother, Kylie Johnson, has been posting regular updates on social media, recently saying she would do anything to just hear Pheobe's voice.
Residents of the Gin Gin property have spoken to officers and are co-operating with police, who are treating her disappearance as suspicious.
Pheobe is about 180cm tall with a pale complexion, long hair that has been dyed red and hazel eyes.
She was last seen carrying luggage, wearing a green tank top and grey sweatpants.
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