A teen boy's body has been found in a creek in Blue Gum Forest at the Blue Mountains National Park. A teen boy’s body has been found in a creek in Blue Gum Forest at the Blue Mountains National Park. Credit: AAP

A teenage boy has been found dead in a National Park creek after he became separated from a mate on a camping trip.

Two boys, aged 16 and 17, travelled to Leura Train Station on Tuesday before they walked to Mount Hay, NSW Police said.

The older boy activated his personal locator beacon shortly before 6pm on Wednesday after the pair became separated.

A multi-agency response was triggered, with the 17-year-old boy winched from the Acacia Flats camping ground, about 36km from Mount Hay.

The search for the 16-year-old continued as rescue helicopters, paramedics and rescue squads scoured the wilderness.

His body was found in a creek in Blue Gum Forest at the Blue Mountains National Park about 1pm on Thursday.

“A post-mortem examination will be conducted in coming days to determine the cause of death, and a report will be prepared for the information of the coroner,” NSW Police said.