The search for missing teenager Cassie Olczak in bushland on Sydney's southern outskirts has wrapped up for the day with police still hopeful of finding her.
Helicopters, trail bikes, the dog squad and about 40 volunteers started scouring the Royal National Park on Wednesday.
The search was triggered after CCTV vision was discovered of the 16-year-old at Waterfall Station about 7pm on Sunday, the day she went missing.
Cassie went missing after visiting friends a day after returning to Australia from a trip to see her father in Abu Dhabi.
Police believe she may have taken a substance before she went missing and been disoriented from jet-lag.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Inspector Jeff Dean said the search would recommence in the morning.
"We have searched numerous tracks in the national park," he told AAP.
"There is no point going into darkness. The risks outweigh the benefits to that and we will probably recommence tomorrow morning."
A concerned friend had said Cassie was incoherent and needed sleep and to go home to bed before she went missing, her mother said.
Connie Olczak broke down in tears while making a desperate public plea for help to bring her daughter home.
"My gut tells me she's alive, I need help, I'm running out of time," she told reporters.
"If she hears this, your friends and family are desperate for you to come home, please come home."
Ms Olczak has been handing out flyers to commuters and frantically appealing for help through social media this week.
She says her daughter is not street smart and dislikes crowded places, and is a "stunner" who had a modelling contract.
Cassie was due to start a new hairdressing job next week, Ms Olczak told reporters.
Inspector Dean said police were looking for any signs that indicated Cassie had been in the bushland recently, and were speaking to nearby residents for information.
"The last sighting of her was here on Sunday evening so we will do this until we find something new," he said.
"We are always hopeful. We have got a lot of people committed to the search so far and will tomorrow and we all have high hopes of finding her."
The missing teen has not used her bank account or Facebook page since Sunday.
