Police have expanded their search for Pheobe Bishop after items believed to be linked to the investigation were found in southern Queensland's Good Night Scrub National Park.
Pheobe was last seen near Bundaberg airport about 8.30am on May 15 after booking a trip to Western Australia.
She has not been seen or heard from since, with CCTV footage indicating she never entered the airport.
The Good Night Scrub National Park, which is an hour's drive from the airport, has emerged as "crucial" to the investigation, with homicide detectives and police divers called in.
"Some items, believed to be linked to the investigation, have been located during the search and have been seized for forensic examination," a police statement said on Monday.
"Police have now expanded the search area and have renewed their appeal for information after recent investigations show some evidence may have been moved from the Good Night Scrub area, prior to police arrival."
Anyone with information, footage or sightings of a grey Hyundai ix35 between May 15 to 18 in the Gin Gin area should contact police.
Pheobe's mother, Kylie Johnson, on Monday said her family was living in a "cyclone of uncertainty", with her young son asking why his sister wasn't answering their calls.
But she is taking some comfort in the local Gin Gin community's "Leave the Lights On for Pheobe" campaign.
Locals have posted photos on social media of their front door lights switched on "to guide Pheobe home".
"Your little man/brother asked yesterday 'Why won"t Phee take our calls? She always takes our calls!'," Ms Johnson wrote on social media on Monday.
"Mate i wish i knew but we have to believe that the police and the lights that our amazing community are leaving on will ... bring her home to us."
The Gin Gin property near Bundaberg where Pheobe lived with two other people has been declared a crime scene, along with the grey Hyundai thought to have been used to take the teen to the airport.
Queensland Police expanded their search about 40km south of Gin Gin to the Good Night Scrub park.
Ms Johnson said the wait for answers was taking its toll.
"As we enter day 11 of Pheobe still not being home our numbness to our tears, to our hearts breaking and this hell is heavy," she posted on Facebook.
"Not knowing what to say, what to do or even how to continue to live in this cyclone of uncertainty.
"The tears come, the anger and frustrations come and most of all our hearts are shattering more and more each Day."
Queensland Premier David Crisafulli said every effort would be made to support the police search for Pheobe.
"Events like that rock the heart and soul of communities - they always do," he told reporters on Monday.
"We want the community to know that we are thinking about them and we will give every resource that police need to do the job."
Residents of the Gin Gin property where Pheobe lived 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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