Fears for missing 16-year-old who got on a Sydney train but "never got off."

Update: Almost three days after Cassie Olczak was last seen, NSW police are now searching the Royal National Park for the missing Sydney teenager.

The 15-hectare national park is almost 40 minutes away from Banksia railway station, where Olczak was last seen on Sunday night.

A police spokesperson has said further information regarding the search will be provided in this evening’s 6pm news.

Mamamia previously reported… 

The mother of missing Sydney teenager Cassie Olczak says she is “begging for help.”

Missing since Sunday evening, the 16-year-old girl from Sylvania was last seen at approximately 6.30pm after getting off a southbound train at Banksia railway station. She was supposed to be catching a connecting train to Hurstville but has not been seen since.

Three days on, her family’s frantic search continues, with mother Connie Olczak saying her daughter’s disappearance is totally out of character.

The 16-year-old had only arrived home on Saturday night after visiting her father in Abu Dhabi.

Her mother told Fairfax Media “she came off a plane 7pm Saturday night, she came home, she ate, went to bed, was eager to meet up with her friends the next day.

“The next day her sister drove her to her best friend’s house, they said she was fine … as the day went on she was highly agitated and they told her to go home and get some sleep.”

But it was then that Cassie went missing, never arriving home.

Cassie's mother says Cassie is not "street smart." Via Facebook.

Mrs Olczak wrote on Facebook that CCTV shows Cassie boarding the train at Banksia at 6.58pm  but there is no record of her getting off.

Mrs Olczak said that as she made her appeal for Cassie public there had been some leads with an unconfirmed report someone fitting Cassie's description and wearing the same clothing was seen sleeping on the 5:37am train from Blacktown to Emu Plains with a pink blanket.

Her sister, Jaqueline, who was out searching for the night said that she believed Cassie may be dehydrated and jet-lagged.

Cassie had just finished school and is due to begin a TAFE hairdressing course next week.

Her devastated mother told The Daily Mail that Cassie's disappearance was out of character and that she'd never done anything like it before. She said that Cassie wasn't "street smart."

Police are concerned for her welfare. Via Facebook.

Police said there are concerns for her welfare due to her young age.

“Police have conducted extensive inquiries to date to try to locate Cassie, but at this time have been unsuccessful,” NSW Police said in a statement.

“Cassie is described as being of caucasian appearance, about 175cm tall with a thin build and dark brown hair.

She was last seen wearing a multicoloured shirt, grey tights and white and gold Adidas sneakers.”